Auto-braking for an electromagnetic machine

ABSTRACT

Systems and methods are provided for braking a translator of a linear multiphase electromagnetic machine. The system detects a fault event, and in response to detecting the fault event, causes the translator to brake using an electromagnetic technique. Braking includes causing the translator to stop reciprocating, by applying a force opposing an axial motion, which may occur within one cycle, or over many cycles. The fault event may include, for example, a fault associated with an encoder, a controller, an electrical component, a communications link, a phase, or a subsystem. The system includes a power electronics system configured to apply current to the phases. The system may use position information, current information, operating parameters, or a combination thereof to brake. Alternatively, the system need not use position information, current information, and operating parameters, and may brake the translator independent of such information.

The present disclosure is directed towards auto-braking, and moreparticularly towards auto-braking one or more translators of amultiphase electromagnetic machine in response to an event. Thisapplication is a continuation of U.S. patent application Ser. No.16/137,506 filed on Sep. 20, 2018, which claims the benefit of U.S.Provisional Patent Application No. 62/561,166 filed Sep. 20, 2017, U.S.Provisional Patent Application No. 62/561,163 filed Sep. 20, 2017, andU.S. Provisional Patent Application No. 62/561,167 filed Sep. 20, 2017,the disclosures of which are all hereby incorporated by reference hereinin their entireties.

BACKGROUND

Systems that convert between kinetic energy and electrical energy, suchas free piston systems, sometimes require fault management. Typicalmechanically linked systems provide for a fixed trajectory. For example,in a conventional piston engine, energy is transferred to a crankshaftduring an expansion stroke, while it is removed from the crankshaftduring a compression stroke. If a fault occurs, the trajectory isusually maintained, and the moving parts can effectively spool down to astop safely and predictably. Systems that do not include mechanicalconstraints, such as a free-piston machines having linear motors, forexample, conventionally rely on extensive real-time control, and theloss of that control can be catastrophic.

Systems having multiple piston assemblies, such as opposed-pistonengines typically require that the assemblies remain synchronized tosome extent. If aspects of control are lost, or other faults occur,synchronization may suffer, and behavior of the system might becomeunpredictable.

SUMMARY

In some embodiments, the present disclosure is directed to a lineargenerator that includes a linear electromagnetic machine, a powerelectronics system coupled to the plurality of phases and controlcircuitry coupled to the power electronics system. The linearelectromagnetic machine includes a translator and a stator comprising aplurality of phases. The control circuitry configured to detect a faultevent; and in response to detecting the fault event, cause thetranslator of the linear multiphase electromagnetic machine to brake byusing an electromagnetic technique.

In some embodiments, the control circuitry is further configured todetermine the electromagnetic technique in response to detecting thefault event.

In some embodiments, the electromagnetic technique is a firstelectromagnetic technique, and the control circuitry is furtherconfigured to cause, using a second electromagnetic technique, thetranslator of the linear multiphase electromagnetic machine to brake.

In some embodiments, the electromagnetic technique is implemented inhardware or software.

In some embodiments, the control circuitry is further configured todetermine availability information of at least one operating parameterof the linear multiphase electromagnetic machine, and determine theelectromagnetic technique based on the availability information.

In some embodiments, the fault event is associated with one of a faultevent associated with a controller, a fault event associated with anencoder, a fault event associated with a switch coupled to a phase ofthe multiphase electromagnetic machine, a fault event associated with agrid-tie inverter, a fault event associated with a shorted phase of themultiphase electromagnetic machine, a fault event associated withcommunication between one or more control subsystems, and a fault eventassociated with an operating parameter value of the linear multiphaseelectromagnetic machine.

In some embodiments, the control circuitry is further configured todetermine phase current information for at least one phase of the linearmultiphase electromagnetic machine, and the control circuitry is furtherconfigured to cause the translator to brake is based at least in part onthe phase current information.

In some embodiments, the control circuitry is further configured tocause the translator to achieve a reduced position-velocity trajectory.

In some embodiments, the fault event includes an unavailability ofposition information of the translator, and wherein the electromagnetictechnique is independent of position information.

In some embodiments, the translator includes a free-piston assembly.

In some embodiments, the present disclosure is directed to a lineargenerator that includes a linear electromagnetic machine, a powerelectronics system coupled to the plurality of phases and a DC bus, andcontrol circuitry coupled to the power electronics system. The linearelectromagnetic machine includes a translator and a stator comprising aplurality of phases. The power electronics system includes a resistorand at least one switch are coupled in series across the DC bus. Thecontrol circuitry is configured to detect a fault event; and in responseto detecting the fault event, cause the translator of the linearmultiphase electromagnetic machine to brake by closing the at least oneswitch.

In some embodiments, the DC bus is coupled to a grid-tie inverter, andthe control circuitry is further configured to detect a fault associatedwith at least one of the DC bus and the grid-tie inverter.

In some embodiments, each phase of the linear multiphase electromagneticmachine includes a respective first phase lead and a respective secondphase lead. Each first phase lead is coupled to a first side of arespective H-bridge coupled across the DC bus. Each second phase lead iscoupled to a second side of the respective H-bridge across the DC bus.Each first phase lead is coupled by a first respective diode to theresistor, and the first respective diode has a polarity relative to theresistor. Each second phase lead is coupled by a second respective diodeto the resistor, where the respective second diode has the polarityrelative to the resistor. The control circuitry is further configured tocause switches of each first side and switches of each second side ofeach respective H-bridge to remain open.

In some embodiments, each phase of the linear multiphase electromagneticmachine includes a respective first phase lead and a respective secondphase lead. Each first phase lead is coupled to a neutral wyeconnection, each second phase lead is coupled to a side of therespective half H-bridge across the DC bus. Each first phase lead iscoupled by a first respective diode to the resistor, wherein the firstrespective diode has a polarity relative to the resistor. Each secondphase lead is coupled by a second respective diode to the resistor,where the respective second diode has the polarity relative to theresistor. The control circuitry is further configured to cause switchesof each first side and the switches of each respective half H-bridge toremain open.

In some embodiments, the present disclosure is directed to a lineargenerator that includes a linear electromagnetic machine, a powerelectronics system coupled to the plurality of phases, and controlcircuitry coupled to the power electronics system. The linearelectromagnetic machine includes a translator and a stator comprising aplurality of phases. The control circuitry is configured to detect afault event and determine phase current information for a plurality ofphases of the linear multiphase electromagnetic machine. The controlcircuitry is configured to cause the power electronics system to applyto each phase of the plurality of phases a respective current based onthe phase current information; and

in response to detecting the fault event, and determine, for at leastone phase of the plurality of phases, a respective current. The controlcircuitry is configured to cause the power electronics system to applythe respective current to the at least one phase to oppose the motion ofthe translator to cause the translator to brake.

In some embodiments, the translator translates according to a firsttrajectory having a first apex position, and the control circuitry isfurther configured to cause the translator to achieve a second apexposition. The second apex position is closer to a mid-stroke positionthan the first apex position.

In some embodiments, the at least one phase includes at least twophases, and wherein the control circuitry is further configured todetermine a least norm solution for the respective current for each ofthe at least two phases.

In some embodiments, the present disclosure is directed to a lineargenerator that includes a linear electromagnetic machine, a powerelectronics system coupled to the plurality of phases, and controlcircuitry coupled to the power electronics system. The linearelectromagnetic machine includes a translator and a stator comprising aplurality of phases. The control circuitry is configured to detect afault event and determine a polarity indicative of an electromotiveforce (emf) in at least one phase of the linear multiphaseelectromagnetic machine caused by a motion of the translator. Thecontrol circuitry is configured to, in response to detecting the faultevent, cause, based on the polarity, the power electronics system toapply a current to a respective phase of the at least one phase to causea force acting on the translator that opposes an axial motion of thetranslator to cause the translator to brake.

In some embodiments, the control circuitry is further configured todetermine phase current information for the respective phase, anddetermine the polarity based on the phase current information.

In some embodiments, the control circuitry is further configured tocause the power electronics system to short the respective phase for afirst time period, determine phase current information for therespective phase for the first time period, and determine the polaritybased on the phase current information. The control circuitry is furtherconfigured to cause the power electronics system to apply the current tothe respective phase during a second time period that does not overlapwith the first time period.

In some embodiments, the control circuitry is further configured tocause the power electronics system to apply a DC current to therespective phase during a first time period, determine phase currentinformation for the respective phase for the first time period, anddetermine the polarity based on the phase current information. Thecontrol circuitry is further configured to cause the power electronicssystem to apply the current to the respective phase during a second timeperiod that does not overlap with the first time period.

In some embodiments, the control circuitry is further configured tocause the power electronics system to apply the current to therespective phase further based on position information associated withthe translator.

In some embodiments, the control circuitry is further configured tocause the power electronics system to apply the to the respective phasebased on a control signal, and the control circuitry is furtherconfigured to compare the control signal to a threshold to determine thepolarity.

In some embodiments, the present disclosure is directed to a lineargenerator that includes a linear electromagnetic machine, a powerelectronics system coupled to the plurality of phases, and controlcircuitry coupled to the power electronics system. The linearelectromagnetic machine includes a translator and a stator comprising aplurality of phases. The power electronics system is coupled to theplurality of phases and includes a plurality of corresponding H-bridges.Each phase of the linear multiphase electromagnetic machine includes arespective first phase lead and a respective second phase lead. Eachfirst phase lead is coupled to a first side of a respective H-bridgecoupled across a DC bus. The first side includes a high-voltage switchand a low-voltage switch. Each second phase lead is coupled to a secondside of the respective H-bridge across the DC bus. The second sideincludes a high-voltage switch and a low-voltage switch. The controlcircuitry is further configured to detect a fault event, and in responseto detecting the fault event, apply braking signals to the firsthigh-voltage switch, the first low-voltage switch, the secondhigh-voltage switch, and the second low-voltage switch to cause thetranslator to brake.

In some embodiments, the braking signals include a first set of signalsincluding a first signal applied to activate both the first high-voltageswitch and the second high-voltage switch for a first time period, andto open the first high-voltage switch and the second high-voltage switchfor a second time period, and a second signal applied to open both thefirst low-voltage switch and the second low-voltage switch during boththe first time period and the second time period. In some embodiments,the braking signals include a second set of signals including a thirdsignal applied to activate both the first low-voltage switch and thesecond low-voltage switch for a third time period, and to open the firstlow-voltage switch and the second low-voltage switch for a fourth timeperiod, and a fourth signal applied to open both the first high-voltageswitch and the second high-voltage switch during both the third timeperiod and the fourth time period.

In some embodiments, the first signal includes an on-off duty cycle, andwherein the third signal includes an on-off duty cycle.

In some embodiments the braking signals are configured to cause a firststate wherein the first high-voltage switch and the second high-voltageswitch are closed for a first time period. In some embodiments thebraking signals are configured to cause a second state wherein the firstlow-voltage switch and the second low-voltage switch are closed for asecond time period that does not overlap the first time period. In someembodiments the braking signals are configured to cause a third statewherein the first high-voltage switch, the second high-voltage switch,the first low-voltage switch, and the second low-voltage switch are allopen for a third time period that does not overlap the first time periodor the second time period.

In some embodiments, the present disclosure is directed to a lineargenerator that includes a linear multiphase electromagnetic machine, apower electronics system coupled to the plurality of phases, and controlcircuitry coupled to the power electronics system. The linearelectromagnetic machine includes a stator having a plurality of phases.The linear electromagnetic machine also includes a translator having amagnetic section and at least one conductive section axially offset fromthe magnetic section. The magnetic section is axially offset from asubset of phases of the plurality of phases. The control circuitry isfurther configured to detect a fault event and in response to detectingthe fault event, cause the power electronics system to apply to at leastone phase of the subset of phases a respective current configured togenerate an eddy current in the at least one conductive section, whereinthe eddy current generates a force that opposes an axial motion of thetranslator to cause the translator to brake.

In some embodiments, the present disclosure is directed to a method forbraking a translator of a linear multiphase electromagnetic machine. Themethod includes detecting a fault event using circuitry, and in responseto detecting the fault event, causing, using an electromagnetictechnique, the translator of the linear multiphase electromagneticmachine to brake.

In some embodiments, the present disclosure is directed to a method forbraking a translator of a linear multiphase electromagnetic machine,wherein the linear multiphase electromagnetic machine is coupled to a DCbus, and wherein a resistor and at least one switch are coupled inseries across the DC bus. The method includes detecting a fault eventusing circuitry and in response to detecting the fault event, causingthe translator of the linear multiphase electromagnetic machine to brakeby closing the at least one switch.

In some embodiments, the present disclosure is directed to a method forbraking a translator of a linear multiphase electromagnetic machine. Themethod includes detecting a fault event using circuitry, determiningphase current information for a plurality of phases of the linearmultiphase electromagnetic machine, applying to each phase of theplurality of phases a respective current based on the phase currentinformation. In response to detecting the fault event, the methodincludes determining, for at least one phase of the plurality of phases,a respective current, and applying the respective current to the atleast one phase to oppose the motion of the translator to cause thetranslator to brake.

In some embodiments, the present disclosure is directed to a method forbraking a translator of a linear multiphase electromagnetic machine. Themethod includes detecting a fault event using circuitry, determining apolarity indicative of an electromotive force (emf) in at least onephase of the linear multiphase electromagnetic machine caused by amotion of the translator, and in response to detecting the fault event,causing, based on the polarity, a current to be applied to a respectivephase of the at least one phase to cause a force acting on thetranslator that opposes an axial motion of the translator to cause thetranslator to brake.

In some embodiments, the present disclosure is directed to a method forbraking a translator of a linear multiphase electromagnetic machine,wherein each phase of the linear multiphase electromagnetic machineincludes a respective first phase lead and a respective second phaselead, each first phase lead is coupled to a first side of a respectiveH-bridge coupled across a DC bus, wherein the first side comprises ahigh-voltage switch and a low-voltage switch, and each second phase leadis coupled to a second side of the respective H-bridge across the DCbus, wherein the second side comprises a high-voltage switch and alow-voltage switch. The method includes detecting a fault event usingcircuitry and in response to detecting the fault event, applying brakingsignals to the first high-voltage switch, the first low-voltage switch,the second high-voltage switch, and the second low-voltage switch tocause the translator to brake.

In some embodiments, the present disclosure is directed to a method forbraking a translator of a linear multiphase electromagnetic machine,wherein the linear multiphase electromagnetic machine includes a statorcomprising a plurality of phases, and the translator includes a magneticsection and at least one conductive section axially offset from themagnetic section. The magnetic section is axially offset from a subsetof phases of the plurality of phases. The method includes detecting afault event using circuitry and in response to detecting the faultevent, applying to at least one phase of the subset of phases arespective current configured to generate an eddy current in the atleast one conductive section, wherein the eddy current generates a forcethat opposes an axial motion of the translator to cause the translatorto brake.

In some embodiments, the present disclosure is directed to anon-transient computer readable medium including non-transitory computerreadable instructions for braking a translator of a linear multiphaseelectromagnetic machine. The non-transitory computer readableinstructions include an instruction for detecting, using circuitry, afault event and an instruction for, in response to detecting the faultevent, causing, using an electromagnetic technique, the translator ofthe linear multiphase electromagnetic machine to brake.

In some embodiments, the present disclosure is directed to anon-transient computer readable medium including non-transitory computerreadable instructions for braking a translator of a linear multiphaseelectromagnetic machine, wherein the linear multiphase electromagneticmachine is coupled to a DC bus, and wherein a resistor and at least oneswitch are coupled in series across the DC bus. The non-transitorycomputer readable instructions include an instruction for detecting,using circuitry, a fault event and an instruction for, in response todetecting the fault event, causing the translator of the linearmultiphase electromagnetic machine to brake by closing the at least oneswitch.

In some embodiments, the present disclosure is directed to anon-transient computer readable medium including non-transitory computerreadable instructions for braking a translator of a linear multiphaseelectromagnetic machine. The non-transitory computer readableinstructions include an instruction for detecting, using circuitry, afault event, an instruction for determining phase current informationfor a plurality of phases of the linear multiphase electromagneticmachine, an instruction for applying to each phase of the plurality ofphases a respective current based on the phase current information. Inresponse to detecting the fault event the instructions include aninstruction for determining, for at least one phase of the plurality ofphases, a respective current, and an instruction for applying therespective current to the at least one phase to oppose the motion of thetranslator to cause the translator to brake.

In some embodiments, the present disclosure is directed to anon-transient computer readable medium including non-transitory computerreadable instructions for braking a translator of a linear multiphaseelectromagnetic machine. The non-transitory computer readableinstructions include an instruction for detecting, using circuitry, afault event, an instruction for determining a polarity indicative of anelectromotive force (emf) in at least one phase of the linear multiphaseelectromagnetic machine caused by a motion of the translator, and aninstruction for, in response to detecting the fault event, causing,based on the polarity, a current to be applied to a respective phase ofthe at least one phase to cause a force acting on the translator thatopposes an axial motion of the translator to cause the translator tobrake.

In some embodiments, the present disclosure is directed to anon-transient computer readable medium including non-transitory computerreadable instructions for braking a translator of a linear multiphaseelectromagnetic machine, wherein each phase of the linear multiphaseelectromagnetic machine includes a respective first phase lead and arespective second phase lead, and each first phase lead is coupled to afirst side of a respective H-bridge coupled across a DC bus, wherein thefirst side comprises a high-voltage switch and a low-voltage switch.Each second phase lead is coupled to a second side of the respectiveH-bridge across the DC bus, wherein the second side comprises ahigh-voltage switch and a low-voltage switch. The non-transitorycomputer readable instructions include an instruction for detecting,using circuitry, a fault event, and an instruction for, in response todetecting the fault event, applying braking signals to the firsthigh-voltage switch, the first low-voltage switch, the secondhigh-voltage switch, and the second low-voltage switch to cause thetranslator to brake.

In some embodiments, the present disclosure is directed to anon-transient computer readable medium including non-transitory computerreadable instructions for braking a translator of a linear multiphaseelectromagnetic machine. The linear multiphase electromagnetic machineincludes a stator having a plurality of phases. The translator includesa magnetic section and at least one conductive section axially offsetfrom the magnetic section. The magnetic section is axially offset from asubset of phases of the plurality of phases. The non-transitory computerreadable instructions include an instruction for detecting, usingcircuitry, a fault event and an instruction for, in response todetecting the fault event, applying to at least one phase of the subsetof phases a respective current configured to generate an eddy current inthe at least one conductive section, wherein the eddy current generatesa force that opposes an axial motion of the translator to cause thetranslator to brake.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure, in accordance with one or more variousembodiments, is described in detail with reference to the followingfigures. The drawings are provided for purposes of illustration only andmerely depict typical or example embodiments. These drawings areprovided to facilitate an understanding of the concepts disclosed hereinand shall not be considered limiting of the breadth, scope, orapplicability of these concepts. It should be noted that for clarity andease of illustration these drawings are not necessarily made to scale.

FIG. 1 shows a cross-sectional view of a device including two linearelectromagnetic machines, in accordance with some embodiments of thepresent disclosure;

FIG. 2 shows a cross-sectional view of an illustrative linearelectromagnetic machine (LEM), in accordance with some embodiments ofthe present disclosure;

FIG. 3 shows a block diagram of an illustrative system for controlling amultiphase machine, in accordance with some embodiments of the presentdisclosure;

FIG. 4 shows a block diagram of an illustrative arrangement havingdistributed phase control and distributed power management, inaccordance with some embodiments of the present disclosure;

FIG. 5 shows a block diagram of an illustrative arrangement havingdistributed phase control and distributed power management, inaccordance with some embodiments of the present disclosure;

FIG. 6 shows a block diagram of an illustrative arrangement having asingle LEM, distributed phase control and distributed power management,with a partitioned DC bus, in accordance with some embodiments of thepresent disclosure;

FIG. 7 shows a block diagram of an illustrative arrangement having twoLEMs, distributed phase control and distributed power management, with apartitioned DC bus, in accordance with some embodiments of the presentdisclosure;

FIG. 8 shows a block diagram of an illustrative phase control system, inaccordance with some embodiments of the present disclosure;

FIG. 9 shows a flowchart of an illustrative process for managing phasecurrent, in accordance with some embodiments of the present disclosure;and

FIG. 10 shows a flowchart of an illustrative process for managing one ormore failed phase control systems, in accordance with some embodimentsof the present disclosure.

FIG. 11 shows a flowchart of an illustrative process for automaticbraking, in accordance with some embodiments of the present disclosure;

FIG. 12 shows an illustrative arrangement, including a power electronicssystem coupled to a phase of a multiphase electromagnetic machine, inaccordance with some embodiments of the present disclosure;

FIG. 13 shows an illustrative controller for determining a controlsignal, in accordance with some embodiments of the present disclosure;

FIG. 14 shows an illustrative controller for processing output of thecontroller of FIG. 13, in accordance with some embodiments of thepresent disclosure;

FIG. 15 shows a plot of an illustrative energy metric corresponding to amultiphase electromagnetic machine, in accordance with some embodimentsof the present disclosure;

FIG. 16 shows plots of illustrative signals in a shorter timescalecorresponding to a phase of a multiphase electromagnetic machine, inaccordance with some embodiments of the present disclosure;

FIG. 17 shows a flowchart of an illustrative process for managingcurrent in one or more phases of a multiphase electromagnetic machine,in accordance with some embodiments of the present disclosure;

FIG. 18 shows a flowchart of an illustrative process for managingshorting one or more phases of a multiphase electromagnetic machine, inaccordance with some embodiments of the present disclosure;

FIG. 19 shows a flowchart of an illustrative process for managingbraking a translator of a multiphase electromagnetic machine, inaccordance with some embodiments of the present disclosure;

FIG. 20 shows an illustrative system, including a multiphaseelectromagnetic machine, in accordance with some embodiments of thepresent disclosure;

FIG. 21 shows a flowchart of an illustrative process for managingbraking a translator of a multiphase electromagnetic machine based onposition information of the translator, in accordance with someembodiments of the present disclosure;

FIG. 22 shows a flowchart of an illustrative process for positionestimation, in accordance with some embodiments of the presentdisclosure;

FIG. 23 shows a flowchart of an illustrative process for determining apolarity associated with a phase, in accordance with some embodiments ofthe present disclosure;

FIG. 24 shows a block diagram of an illustrative power electronicssystem having a brake resistor and a switch, and one phase of amultiphase machine, in accordance with some embodiments of the presentdisclosure;

FIG. 25 shows a flowchart of an illustrative process for engaging abrake resistor, in accordance with some embodiments of the presentdisclosure;

FIG. 26 shows a block diagram of an illustrative power electronicssystem having a brake resistor, a switch, and a diode pair, and onephase of a multiphase machine, in accordance with some embodiments ofthe present disclosure;

FIG. 27 shows illustrative braking signals for applying to a powerelectronics system, in accordance with some embodiments of the presentdisclosure;

FIG. 28 shows a block diagram of an illustrative power electronicssystem configured to receive braking signals, in accordance with someembodiments of the present disclosure;

FIG. 29 shows a flowchart of an illustrative process for applyingbraking signals, in accordance with some embodiments of the presentdisclosure;

FIG. 30 shows a cross-sectional view of a stator and a translator,configured for linear eddy current braking, in accordance with someembodiments of the present disclosure;

FIG. 31 shows a flowchart of an illustrative process for engaging aneddy current brake, in accordance with some embodiments of the presentdisclosure; and

FIG. 32 shows illustrative position-velocity trajectories associatedwith a translator, in accordance with some embodiments of the presentdisclosure.

DETAILED DESCRIPTION

The present disclosure is directed to electromagnetic machines. Forexample, an electromagnetic machine may include a stator having one ormore phases.

In some embodiments, the present disclosure is directed to automaticallybraking a translating assembly of an electromagnetic machine in responseto an event such as a fault event (e.g., a controller stops receivingsignals from the central control unit, or a position encoder for thetranslating assembly stops producing a signal to a central controlunit). “Braking”, as used herein, is the act of causing a trajectory(e.g., a position-velocity trajectory) of a translator to reduce instroke, peak velocity, or both. For example, braking may includeapplying current to phases of a multiphase electromagnetic machine toproduce a force on a translator that opposes motion of the translator(e.g., thereby slowing it down by extracting energy in the form ofelectrical work), which acts to shrink the trajectory. In a furtherexample, braking may include removing kinetic energy from a translator,actively or passively, which may act to shrink the trajectory of thetranslator. It will be understood that under normal operation, theelectromagnetic force on a translator may oppose motion to extractelectrical energy from kinetic energy. Braking can be distinguished fromnormal operation by the intent to reduce a translator stroke, reduce atranslator velocity, decelerate a translator, remove energy from atranslator, or otherwise bring the translator to rest, near rest, or anotherwise reduced-power operating condition. For example, during normaloperation, a translator may achieve a zero velocity at ends of thestroke, and a maximum velocity near the middle of the stroke. Normaloperation is typically directed to repeating a set of strokes, definingcycles, to provide a consistent power output (e.g., whether steady ortransient). Braking is typically directed to bringing a translatortowards a stop, as a result of an indication to shut down (e.g., formaintenance, to avoid damage, or in response to an event such as afault). For example, the descriptions of FIGS. 11-30 provideillustrative examples of braking systems and techniques for brakingmultiphase systems.

In some embodiments, the present disclosure is directed to distributingcomponents, control, or both, among phases, rather than grouping manyphases together. For example, a stator may include thirty windingscorresponding to thirty iron cores. Rather than grouping many windingstogether (e.g., six groups of five phases), each winding and iron coremay be treated as a phase to provide better spatial resolution of phasecurrents (e.g., thirty phase currents rather than six phase currents inthe grouped case). Further, any suitable components of the electricalnetwork may be distributed to these phase control systems to providerobustness and reliability. For example, the descriptions of FIGS. 4-10provide illustrative examples of controls and arrangements of multiphasesystems.

A linear electromagnetic machine (LEM) may include a high number ofwindings (e.g., thirty windings) and a number of phases that are atleast two to three times greater (e.g., six phases to nine phases) thanthe number of phases in conventional LEM designs (e.g., three phases). ALEM may include windings, which may optionally be coupled in series intogroups, forming corresponding phases (e.g., five windings per phase forsix phases, or one winding per phase for thirty phases). Groupingwindings in series into phases reduces the number of control electronicsand power transistors needed to operate the LEM. However, a reduction inthe number of components may increase reliability concerns.

Grouping the windings also means that each grouped winding has the samecurrent, which may be non-ideal in a LEM. For example, it may be desiredfor a phase control system to apply time-phased currents to the windingsto more optimally generate electromagnetic force based on a translator'sinstantaneous position, which changes in time during operation. In thepresent disclosure, windings may be ungrouped, or grouped to anysuitable extent, to provide spatial resolution, robustness, andreliability of the provided LEM.

In some embodiments, the present disclosure may be applied to multiphaseelectromagnetic machines. For example, in some embodiments, the presentdisclosure describes a LEM that includes a large number of windings. Itwill be understood that a large number of phases refers to a number ofphases in excess of conventional LEM designs (e.g., three phases). Theterms “winding,” “phase,” and “group” are used herein to describeaspects of a LEM.

A “winding” refers to a continuous, electrically conductive wirewrapping around one or more iron cores, having a single current whichmay be applied (e.g., regardless of control, the same current isapplied). As used herein, the term “winding” is defined by a state ofhardware. For example, a winding may include copper wire wound around asingle iron core, having two terminal ends to which voltage may beapplied. In a further example, a winding may include a contiguous lengthof copper wire wound around several iron cores in series, having twoterminal ends to which voltage may be applied. In a further example, awinding may include several lengths of copper wire wound around severalcorresponding iron cores, and crimped together in series (e.g., using abutt-splice connector or other suitable connector) to have two terminalends to which voltage may be applied. In an illustrative example, astator of a LEM may include thirty windings and thirty correspondingiron cores, with sixty terminal ends (i.e., thirty pairs) to whichvoltage may be applied. Windings may be combined (e.g., a terminal endof one winding may be hardwired to a terminal end of another winding) orseparated (e.g., a continuous wrapping of copper wire around severalteeth may be cut in between the teeth to create separate windings).

A “phase” refers to a winding, or group of windings, that can becontrolled individually (e.g., to which a unique phase current can beapplied). To illustrate, a phase may refer to the number of individuallycontrollable N/S pole pairs of a stator. As used herein, the term“phase” is defined by a state of control (e.g., how current is applied).For example, phases may be coupled by a wye neutral, and interact withone another (e.g., not necessarily independent, but rather part of anetwork), but still be controlled individually. A phase is useful, forexample, to describe time behavior of an applied current to one or morephases. As a translator moves relative to a stator, the “phasing” ofcurrents in the phases determines the instantaneous current applied toeach phase. For example, a winding may include copper wire wound arounda single iron core, and that winding may correspond to a phase if it canbe controlled independently (e.g., by a dedicated phase control system).In a further example, a winding may include a continuous length ofcopper wire wound around several iron cores in series, and the entirelength of wire and the cores correspond to a phase. It is apparent thatthe number of phases in a LEM is equal to or less than the number ofwindings in the LEM.

A “group,” in the context of windings and phases, refers to more thanone item combined in some way. A group of windings refers to windingsconnected together such that a single current may be applied. A group ofphases refers to phases that are controlled to act as a single phase byapplying the same current at the same time. Accordingly, a group ofwindings refers to a state of hardware, and a group of phases refers toan aspect of control.

FIG. 1 shows a cross-sectional view of illustrative device 100,including two linear electromagnetic machines 150 and 155, in accordancewith some embodiments of the present disclosure. Free-piston assemblies110 and 120 (i.e., also called translators) include respective pistons112 and 152, respective pistons 182 and 187, and respective translatorsections 151 and 156. Device 100 includes cylinder 130, having bore 132,which may, for example, house a high-pressure section (e.g., acombustion section) between pistons 112 and 152.

In some embodiments, device 100 includes gas springs 180 and 185, whichmay be used to store and release energy during a cycle in the form ofcompressed gas (e.g., a driver section). For example, free-pistonassemblies 110 and 120 may each include respective pistons 182 and 187in contact with respective gas regions 183 and 188 (e.g., high-pressureregions).

Cylinder 130 may include bore 132, centered about axis 170. In someembodiments, free-piston assemblies 110 and 120 may translate along axis170, within bore 132, allowing the gas region in contact with pistons112 and 152 to compress and expand.

In some embodiments, free-piston assemblies 110 and 120 includerespective translator sections 151 and 156 (e.g., which may includemagnets), which interact with respective stators 152 and 157 (e.g.,controlled by a power electronics system) to form respective LEMs 150and 155. For example, as free-piston assembly 110 translates along axis170 (e.g., during a stroke of an engine cycle), translator section 151may induce current in windings of stator 152. Further, current may besupplied to respective windings of stator 152 to generate anelectromagnetic force on free-piston assembly 110 (e.g., to affectmotion of free-piston assembly 110). Braking refers to the applicationof a force to a translator that opposes an axial motion of thetranslator (e.g., along axis 170 as shown in FIG. 1), to reduce atrajectory, slow reciprocation to a stop, or otherwise remove kineticenergy from a translator to significantly slow, or stop, the system(e.g., stop device 100). In some embodiments, a control system isconfigured to provide synchronization between translators 110 and 120,during normal operation, braking, or both. In some embodiments, duringbraking, energy is extracted from one or more translators without regardto efficiency, optimal control, or other constraints that may be ineffect during normal operation. For example, tolerances between desiredand achieved operating parameter values (e.g., a desired and achievedapex position) may be loosened during braking.

FIG. 2 shows a cross-sectional view of illustrative LEM 200, includingstator 210 and translator section 204, in accordance with someembodiments of the present disclosure. Translator section 204 may beconfigured to move along axis 290, relative to stator 210. Stator 210includes a plurality of windings (e.g., winding 234), wound aroundcorresponding ferrous cores (e.g., iron core 236). A phase refers to agroup of one or more iron cores and corresponding windings, to which asingle current is applied. Accordingly, a phase may include any suitablenumber of cores and corresponding windings, which may be, for example,coupled in series. A phase control system (e.g., included in a motorcontroller or control system) may be configured to apply current, via acorresponding power electronics system, to each respective phase. Toillustrate, exemplary phase 280 includes five iron cores and fivewindings (e.g., one of which is winding 225), which may be coupled inseries. To illustrate further, each winding may correspond to arespective phase (e.g., no windings are grouped or wound together inseries). Accordingly, a single current may be applied to the fivewindings (i.e., because they are connected in series). Any suitableconfiguration of windings, grouped into any suitable number of phases,may be used in accordance with the present disclosure. To furtherillustrate, exemplary phase 281 includes three iron cores and threewindings, which may be coupled in series.

The iron cores and windings of stator 210 are configured to generate amagnetic field causing a net electromagnetic force on translator section204, when translator section 204 overlaps the cores axially. The netelectromagnetic force may be oriented in a direction substantiallyparallel to axis 290. For example, referencing FIG. 2 and theillustrated relative position of translator section 204, windings 211,212, and 219 (e.g., corresponding to one or more phases) may interactelectromagnetically with translator section 204. However, at theillustrated position, the phase corresponding to winding 225 (e.g.,illustrative phase 280) does not have a substantially strongelectromagnetic interaction with translator section 204. As translatorsection 204 moves to the right, eventually it will axially overlap withwinding 225, and accordingly the phase corresponding to winding 225 willbe able to more substantially electromagnetically interact withtranslator section 204. As an illustrative example, as translatorsection 204 axially moves over a winding, a back electromotive force(back emf) is generated in the winding, and an electromotive force maybe applied to translator section 204 as a result of current flow in thewinding.

Translator section 204, as shown in FIG. 2, includes an array ofmultiple permanent magnets arranged axially (relative to axis 290), withpolarity indicated as North “N” or South “S.” It will be understood thatthe magnet array of FIG. 2 is an illustrative example, and that atranslator may include any suitable arrangement of permanent magnets, ormay include no permanent magnets (e.g., an induction electromagneticmachine). As translator section 204 moves along axis 290 relative tostator 210, current may flow through windings of one or more phases.

As shown in FIG. 2, assuming each winding corresponds to a phase, stator210 includes thirty phases. Also, as shown in FIG. 2, translator section204 includes fourteen magnet poles. As shown in FIG. 2, the axialalignment of phase one (i.e., corresponding to winding 211) and magneticpole 260 is different from the axial alignment of phase five (i.e.,corresponding to winding 235) and magnetic pole 261. Accordingly,applying the same current in phase one and phase five will notnecessarily be the best current for the position of one or both of themagnets. For example, the relative difference in alignment of phases oneand five with respective magnetic poles 260 and 261 may correspond to adifference in effective force constants (e.g., electromagnetic forcedivided by current) for phases one and five at the shown position oftranslator 204. Phases in a permanent magnet motor must be properlycommutated to achieve force. This commutation can be achievedelectronically by measuring or estimating the position of magnetsrelative to phases.

FIG. 3 shows a diagram of illustrative system 300, in accordance withsome embodiments of the present disclosure. System 300 includesmultiphase machine 340, power electronics system 330, control system350, and grid-tie inverter 320. System 300 may be referred to as alinear generator. It will be understood that while shown separately inFIG. 3, multiphase machine 340 and power electronics system 330 may beintegrated, or otherwise combined to any suitable extent. For example,in some embodiments, multiphase machine 340 and power electronics system330 may be affixed to a frame separately, coupled by phase leads 335. Ina further example, in some embodiments, power electronics system 330 maybe integrated as part of multiphase machine 340. In a further example,multiphase machine 340 may include a stator having a plurality of phasesand a translator (e.g., and other suitable components such as cylinders,bearings, plumbing, etc.), with phase leads 335 that are coupled to DCbus 325 by power electronics system 330.

Multiphase machine 340 may include a system similar to that shown inFIG. 1 (e.g., a free-piston generator), for example. In general,multiphase machine 340 may include one or more translating assemblies(i.e., “translators”) which may undergo reciprocating motion relative tocorresponding one or more stators under the combined effects of gaspressures and electromagnetic forces. The translators may, but need not,include permanent magnets, which may generate a back electromotive force(emf) in phases of the respective stator. It will be understood that, asused herein and as widely understood, back electromotive force refers toa voltage (e.g., causing a current that opposes the current due to anapplied phase voltage). Power electronics system 330 are configured toprovide current to the phases of the stators. For example, powerelectronics system 330 may expose phase leads of phases of the stator toone or more buses of a DC bus, a neutral, a ground, or a combinationthereof.

Power electronics system 330 may include, for example, switches (e.g.,insulated gate bipolar transistors (IGBTs), metal oxide semiconductorfield effect transistor (MOSFET)), diodes, current sensors, voltagesensors, circuitry for managing PWM signals, any other suitablecomponents, or any suitable combination thereof. For example, powerelectronics system 330 may include one or more H-bridges, or other motorcontrol topology of switches for applying current to one or more phases.In some embodiments, power electronics system 330 may interface withmultiphase machine 340 via phase leads 335 which couple to windings ofthe stators, and power electronics system 330 may interface withgrid-tie inverter 320 via DC bus 325 (e.g., a pair of buses, one bus ata higher voltage relative to the other bus). Bus 322 and bus 324together form DC bus 325 in system 300. For example, bus 322 may be atnominally 800V relative to 0V of bus 324 (e.g., bus 322 is the “high”and bus 324 is the “low”). Bus 322 and bus 324 may be at any suitable,nominal voltage, which may fluctuate in time about a mean value, inaccordance with the present disclosure. Accordingly, the term “DC bus”as used herein shall refer to a pair of buses having a roughly fixedmean voltage difference, although the instantaneous voltage mayfluctuate, vary, exhibit noise, or otherwise be non-constant.

Grid-tie inverter 320 may be configured to manage electricalinteractions between AC grid 321 (e.g., three-phase 480 VAC) and DC bus325. In some embodiments, grid-tie inverter 320 is configured to provideelectrical power to AC grid 321 from multiphase machine 340 (e.g., afree-piston engine) via power electronics system 330. In someembodiments, grid-tie inverter 320 may be configured to sourceelectrical power from AC grid 321 to input to multiphase machine 340(e.g., a free-piston air compressor) via power electronics system 330.In some embodiments, grid-tie inverter 320 manages electrical power inboth directions (e.g., to and from AC grid 321). In some embodiments,grid-tie inverter 320 rectifies AC power from AC grid 321 to supplyelectrical power over DC bus 325. In some embodiments, grid-tie inverter320 converts DC power from DC bus 325 to AC power for injecting into ACgrid 321. In some embodiments, grid-tie inverter 320 generates ACwaveforms of current and voltage that are suitable for AC grid 321. Forexample, grid-tie inverter 320 may manage a power factor, frequency,voltage, or combination thereof of AC power injected into AC grid 321.

Although shown as being coupled to AC grid 321 in FIG. 3, grid-tieinverter 320 may be coupled directly to a load, a power source, anothergenerator system, another grid-tie inverter, any other suitable electricpower system, or any combination thereof. For example, generator system300 may be in “islanding” mode or “stand-alone” mode, wherein AC grid321 may be a local AC grid, having an AC load. In some embodiments,generator system 300 need not include GTI 320, and may be configured fora direct DC application (e.g., a DC grid). For example, DC bus 325 maybe coupled to a DC grid, DC load, or any other suitable DC electricalarchitecture.

FIGS. 4-7 illustrate various arrangements of LEMs, phase controlsystems, grid-tie inverters, DC buses, electrical components, and ACgrids. Arrangements 400, 500, 600, and 700 of FIGS. 4-7 are illustrativeembodiments of the present disclosure, and may be combined, appended,truncated, or otherwise suitably modified in accordance with the presentdisclosure. Further, the components shown in FIGS. 4-7 may be combined,appended, truncated, or otherwise suitably modified in accordance withthe present disclosure.

It will be understood that the topology of arrangements 400, 500, 600,and 700 of FIGS. 4-7 need not represent actual physical geometries of alinear generator. For example, referencing FIG. 4, phases one through Nmay be aligned along the axis of each of LEMs 402 and 404, but are shownpartitioned into rows of even and odd phases to simplify the illustratedarrangement of phase control systems. Similarly, the actual spatialarrangement of phase control systems may assume any suitable regular orirregular configuration (e.g., arranged in a line, array, or star).Further details regarding phase control systems are described, forexample, in the context of FIG. 8.

FIG. 4 shows a block diagram of illustrative arrangement 400 havingdistributed phase control and distributed power management, inaccordance with some embodiments of the present disclosure. Arrangement400 includes LEMs 402 and 404, AC grid 494, grid-tie inverters 478 and479, two DC buses, and phase control systems 406, 408, 410, 412, 414,416, 418, 420, 438, 440, 442, 444, 446, 448, 450, and 452.

LEMs 402 and 404 each include multiple phases, each phase including oneor more windings. As shown in FIG. 4, LEMs 402 and 404 each include Nphases, wherein N is an integer greater than three. For example, LEM 402includes N phases, including phase 426 (i.e., an end phase) and phase428. For example, LEM 404 includes N phases, including phase 458 (i.e.,an end phase) and phase 460. Each phase of LEMs 402 and 404 correspondsto a phase control system. For example, phases 422, 424, 426, 428, 454,456, 458 and 460 correspond to phase control systems 406, 410, 414, 418,438, 442, 446, and 450, respectively. Although not shown in FIG. 4, LEMs402 and 404 include corresponding translator sections (e.g., magnetsections).

Phase control systems 406, 408, 410, 412, 414, 416, 418, 420, 438, 440,442, 444, 446, 448, 450, and 452 are configured to manage theapplication of current to corresponding phases. Each phase controlsystem is coupled to a DC bus. For example, a first DC bus is formedfrom bus 474 and bus 476. In a further example, a second DC bus isformed from bus 470 and bus 472. Phase leads 430 and 432 correspond tophase control system 420, which is coupled to a DC bus by leads 434 and436. Phase leads 462 and 464 correspond to phase control system 452,which is coupled to a DC bus by leads 466 and 468.

Grid-tie inverters 478 and 479 are configured to manage electrical powerinteractions between respective DC buses and AC grid 494, as well asmanage a voltage and/or other characteristics of the respective DCbuses. AC grid 494, as shown in FIG. 4, includes a three-phase AC grid(e.g., a 480 VAC 3-phase power supply). Grid-tie inverter 478 is coupledto AC leads 482, 484, and 486 of AC grid 494. Grid-tie inverter 479 iscoupled to AC leads 488, 490, and 492 of AC grid 494. In someembodiments, AC leads 482, 484, and 486 and AC leads 488, 490, and 492may be coupled to separate breakers, fuses, or otherwise AC circuits. Insome embodiments, AC leads 482, 484, and 486 and AC leads 488, 490, and492 may be coupled to the same breakers, fuses, or otherwise ACcircuits. Although not shown in FIG. 4, in some embodiments, grid-tieinverters 478 and 479 may be distributed among, or included as a partof, the phase control systems in the form of smaller-capacity grid-tieinverters, for example. In arrangements where the number of grid-tieinverters is different than the number of phases, but greater than one,the DC bus interconnections to phase control systems may be designed toavoid the complete loss of control of any entire LEMs (i.e., all phasesof the LEM) in the event of a grid-tie inverter failure.

In some embodiments, arrangement 400 provides robustness againstfailures of one DC bus. For example, in the event that the DC bus formedfrom bus 474 and 476 fails, every other phase of LEMs 402 and 404 (i.e.,even-numbered phases two, four, etc.) may still be operational using theDC bus formed from buses 470 and 472. Accordingly, phase control systems406, 408, 410, and 412 may still provide control authority overcorresponding phases of LEM 402 (e.g., allowing position and/or forcecontrol). Further, phase control systems 438, 440, 442, and 444 maystill provide control authority over corresponding phases of LEM 404(e.g., allowing position and/or force control). Similarly, if the DC busformed from buses 470 and 472 fails, phase control systems 414, 416,418, 420, 446, 448, 450, and 452 that are coupled to the DC bus formedfrom buses 474 and 476 may still provide control authority.

For example, the redundancy provided by arrangement 400 may be usefulfor maintaining control in the event of a DC bus failure, a failure ofone grid-tie inverter (e.g., either grid-tie inverter 478 or 479, butnot both), or both. In some embodiments, if one of grid-tie inverters478 and 479 fails, the linear generator is still able to function atnominally half-load, using half of the LEMs' phases (i.e., N/2 as shownin FIG. 4, if N is even). This functionality may, for example, allowcontinued operation, controlled shutdown, auto-braking, or a combinationthereof. Accordingly, each grid-tie inverter need not be a single pointof complete failure for the entire system.

In a further example, the use of multiple phase control systems per LEMmay allow for continued operation in the event that a single phase,phase control system, or component thereof undergoes a partial orcomplete failure. For example, if windings of a particular phase such asphase 428 become shorted (e.g., to the ferrous cores or othercomponents), the particular phase may be isolated by corresponding phasecontrol system 418 ceasing to apply current. Such continued operationmay allow for power production, safe shutdown, or other operation in theevent of a phase short or component failure.

FIG. 5 shows a block diagram of illustrative arrangement 500 havingdistributed phase control and distributed power management, inaccordance with some embodiments of the present disclosure. Arrangement500 includes LEMs 502 and 504, AC grid 546, grid-tie inverters 542 and544, two DC buses, and phase control systems 510, 512, 512, 514, 516,522, 524, 526, and 528. Arrangement 500 differs from arrangement 400 inthat the loss of a single grid-tie inverter may affect all phases of acorresponding LEM (e.g., LEM 502 or 504), but not the other LEM.Although not shown in FIG. 5, in some embodiments, grid-tie inverters542 and 544 may be distributed among, or included as a part of, thephase control systems in the form of smaller-capacity grid-tie inverters(e.g., grid-tie inverters 542 and 544 need not be included in someembodiments). Accordingly, the loss of a grid-tie inverter in such adistributed scheme may allow for some phases to still operate if onephase of a LEM were to fail.

LEMs 502 and 504 each include multiple phases, each phase including oneor more windings. As shown in FIG. 5, LEMs 502 and 504 each include Nphases, wherein N is an integer greater than three. For example, LEM 502includes N phases, including phase 506 (i.e., an end phase) and phase508. For example, LEM 504 includes N phases, including phase 510 (i.e.,an end phase) and phase 512. Each phase of LEMs 502 and 504 correspondsto a phase control system. For example, phases 506, 508, 510 and 512correspond to phase control systems 550, 554, 562, and 566,respectively.

Phase control systems 550, 552, 554, 556, 562, 564, 566, and 568 areconfigured to manage the application of current to corresponding phases.Each phase control system is coupled to a DC bus. For example, a firstDC bus is formed from bus 534 and bus 536. In a further example, asecond DC bus is formed from bus 538 and bus 540. Phase control system556 is coupled to a DC bus by leads 518 and 520. Phase control system568 is coupled to a DC bus by leads 530 and 532.

Grid-tie inverters 542 and 544 are configured to manage electrical powerinteractions between respective DC buses and AC grid 546, as well asmanage a voltage and/or other characteristics of the respective DCbuses. AC grid 546, as shown in FIG. 5, includes a three-phase AC grid(e.g., a 480 VAC 3-phase power supply). In some embodiments, a singlegrid-tie inverted is used to manage both DC buses. For example, in someembodiments, only one of grid-tie inverters 542 and 544 is included.

For example, the use of multiple phase control systems per LEM may allowfor continued operation in the event that a single phase, phase controlsystem, or component thereof undergoes a partial or complete failure.For example, if windings of a particular phase such as phase 506 becomeshorted (e.g., to the ferrous cores or other components), the particularphase may be isolated by corresponding phase control system 550 ceasingto apply current. Such continued operation may allow for powerproduction, safe shutdown, or other operation in the event of a phaseshort or component failure.

In the event of a failure of either of grid-tie inverter 542 andgrid-tie inverter 544, an entire LEM will be impacted (e.g., be renderedwithout access to a DC bus), although the other LEM may maintain accessto a DC bus. For example, if grid-tie inverter 542 experiences afailure, LEM 502 is rendered without a DC bus. Further, if grid-tieinverter 544 is still operational, then LEM 504 may benefit fromcontinued operation of grid-tie inverter 544. For example, without a DCbus, little force may be applied to a translator of LEM 502, but enoughforce may be applied to a translator of LEM 504 to maintainsynchronization of the translators (e.g., a desired trajectory of thetranslators in time). Synchronization may, for example, preventmechanical damage, undesirable engine behavior, or unpredictable enginebehavior.

FIG. 6 shows a block diagram of illustrative arrangement 600 includingLEM 602, distributed phase control and distributed power management,with partitioned DC bus 608, in accordance with some embodiments of thepresent disclosure. Arrangement 600 includes LEM 602, AC grid 606,grid-tie inverter 604, DC buses 608, 614, and 616, components 610 and612, and phase control systems 616, 618, 620, 622, 624, and 626.Arrangement 600 differs from arrangements 400 and 500 of FIGS. 4-5 inthat DC bus 608 managed by grid-tie inverter 604 is portioned in tofirst DC bus 614 and second DC bus 616 using components 610 and 612. Thevoltage of DC bus 608 is distributed to DC buses 614 and 616.Arrangement 600 may be extended to two LEMs by repeating the componentsshown in FIG. 6, in accordance with the present disclosure. For example,a second grid-tie inverter, two more components (e.g., similar tocomponents 610 and 612, or not), and N more phase control systems may beincluded.

In an illustrative example, arrangement 600 may include DC bus 608maintained by grid-tie inverter 604, but phase control systems aresupplied with power from DC buses 614 and 616. In some embodiments,components 610 and 612 include, for example, energy storage devicesconfigured to operate at nominally half the voltage of DC bus 608. Forexample, DC buses 614 and 616 may each be nominally 380 VDC when DC bus608 is nominally 760 VDC. The voltage balance between DC buses 614 and616 may be controlled by adjusting (e.g., continuously, orintermittently) the portion of energy extracted by the correspondingphases (e.g., odd or even phases as shown in FIG. 6). Further, thevoltage balance between DC buses 614 and 616 may be controlled by addinga DC-DC converter between components 610 and 612 (e.g., 380V capacitorbanks in some embodiments).

LEM 602 includes N phases, with each phase including one or morewindings. For example, in some embodiments, N may be thirty or more.Each phase of LEM 602 corresponds to a phase control system. Forexample, phases 651, 652, 653, 654, 655, 657, and 658 correspond tophase control systems 616, 618, 620, 622, 624, and 626, respectively.Although LEM 602 is illustrated with a plurality of phases, a LEM mayinclude one phase, or more than one phase.

Phase control systems 616, 618, 620, 622, 624, and 626 are configured tomanage the application of current to corresponding phases. Each phasecontrol system is coupled to either DC bus 614 or 616, with adjacentphases being coupled to different DC buses. For example, as shown inFIG. 6, phases 651, 653, and 657 are coupled to DC bus 614, while phases652, 654, and 658 are coupled to DC bus 616.

Components 610 and 612 are configured to accommodate fluctuations inelectric power in DC buses 614 and 616. In some embodiments, either orboth of components 610 and 612 may include an energy storage device suchas, for example, a battery, a capacitor, a capacitor bank, or any othersuitable device for storing and releasing electric energy on time scalesrelevant for the operation of LEM 602.

FIG. 7 shows a block diagram of illustrative arrangement 700 includingLEMs 702 and 704, distributed phase control and distributed powermanagement, with partitioned DC bus 746, in accordance with someembodiments of the present disclosure. Arrangement 700 includes LEMs 702and 704, AC grid 744, grid-tie inverter 742, DC buses 746, 748, and 750,components 752 and 754, and phase control systems 710, 712, 714, 716,722, 724, 726, and 728. Arrangement 700 differs from arrangement 600 ofFIG. 6 in that each phase of a particular LEM is coupled to the same DCbus. For example, phase control systems 710, 712, 714, and 716corresponding to LEM 702 are coupled to DC bus 748, while phase controlsystems 722, 724, 726, and 728 corresponding to LEM 704 are coupled toDC bus 750. Further, DC bus 746 is formed from buses 738 and 740.

In an illustrative example, arrangement 700 may include DC bus 746maintained by grid-tie inverter 742, but phase control systems aresupplied power by DC buses 748 and 750. For example, DC buses 748 and750 may each be nominally 380 VDC when DC bus 746 is nominally 760 VDC.The voltage balance between DC buses 748 and 750 may be controlled byadjusting (e.g., continuously, or intermittently) the portion of energyextracted by the corresponding phases (e.g., phases of a particular LEMas shown in FIG. 7). Further, the voltage balance between DC buses 748and 750 may be controlled by adding a DC-DC converter between components752 and 754 (e.g., 380V capacitor banks in some embodiments).

LEMs 702 and 704 each include N phases, where N is an integer greaterthan three, with each phase including one or more windings. For example,in some embodiments, N may be thirty or more. Each phase of LEM 602corresponds to a phase control system.

Phase control systems 710, 712, 714, 716, 722, 724, 726, and 728 areconfigured to manage the application of current to corresponding phasesof LEMs 702 and 704. Each phase control system is coupled to either DCbus 748 or 750, with phases in either LEM being coupled to the same DCbus. Phase leads 734 and 736 correspond to phase control system 716,which is coupled to DC bus 748 by leads 730 and 732.

Components 752 and 754 are configured to accommodate fluctuations inelectric power in DC buses 748 and 750. In some embodiments, either orboth of components 752 and 754 may include an energy storage device suchas, for example, a battery, a capacitor, a capacitor bank, or any othersuitable device for storing and releasing electric energy on time scalesrelevant for the operation of LEMs 702 and 704.

Although not shown in FIG. 7, it may be desired to include a DC-DCconverter to balance energy between components 752 and 754. For example,when maintaining synchronization of translators of LEMs 702 and 704, theenergy balance at any time is not necessarily equal. To illustrate, ifmore power is extracted from one of LEM 702 and 704 than the other, thevoltages across DC buses 748 and 750 may diverge from each other.

FIG. 8 shows a block diagram of illustrative phase control system 800,in accordance with some embodiments of the present disclosure. Phasecontrol system 800, as shown illustratively in FIG. 8, includes phasecontroller 802, power electronics 804, brake resistor 806, power-outputleveler 808, grid-tie inverter 810, position estimator 812, and powersupply 814. In some embodiments, each phase control system (e.g.,similar to phase control system 800) controls an application of currentto a single phase of a multiphase LEM. Further, each phase controlsystem may include elements of the overall electrical system distributedto each phase control system.

In some embodiments, phase controller 802 is configured to controlcurrent in a corresponding phase. In some embodiments, a desired orcommanded current to be applied to the corresponding phase is calculatedlocally by phase controller 802. In some embodiments, a desired orcommanded current to be applied to the corresponding phase iscommunicated from a central controller, which is determining currents tobe applied on all the phases. For example, the desired or commandedcurrent to be applied to the corresponding phase may be determined toalign a measured magnet or translator position, to achieve a total LEMforce (e.g., summed from the electromagnetic force applied by eachphase), or both. In some embodiments, if a sufficiently fast switchingfrequency is used, then phase controller 802 may execute a singlefeedback loop with high bandwidth and fast switching frequency. Forexample, a sufficiently fast switching frequency may be achieved using,but not limited to, any one or more of the following techniques: fastswitching semiconductor devices, soft-switching or resonant converterarrangements, or a combination thereof. In an illustrative example, fastswitching may refer to switching at high enough frequency to avoid anovercurrent or current ripple. In a further illustrative example, a fastswitching frequency may be 10 kHz or faster.

In some embodiments, phase controller 802 is configured to sensemagnetic flux in the corresponding phase. For example, phase controller802 may sense the phase's magnetic flux and use the sensed flux as acontrol feedback. In some such embodiments, phase controller 802 neednot include a current sensor or be configured to receive input from acurrent sensor. Further, in some such embodiments, phase controller 802includes a current sensor with relatively reduced performance,requirements, cost, or a combination thereof. In an illustrativeexample, phase controller 802 may be configured to determine flux basedon the relation V=N (dflux/dt), using a measured voltage V and knownturn count N of the phase winding.

In some embodiments, the current applied to, or voltage applied across,each phase is controlled locally (i.e., by an instance of phase controlsystem 800) to any suitable degree. In some embodiments, phasecontroller 802 may execute a local control loop on phase current. Forexample, a current command may be communicated over a communication linkfrom a central controller to phase controller 802. The communicationlink may include hardware and software for communicating, for example,an analog signal, a digital signal (e.g., using a serial peripheralinterface (SPI)), a CANbus signal, a Modbus signal, an Ethernet signal,any other suitable signal, or any combination thereof. In someembodiments, local control is very fast since the current loop is fast(e.g., low computation times). Any suitable part of the controlmechanism may also be distributed in accordance with the presentdisclosure. For example, a position measurement may be distributed toevery phase and each phase controller 802 may determine desired positionand force to determine a current command, which may be applied by powerelectronics 804. Distributed control is applicable to, for example,maintaining an auto-braking algorithm (e.g., allowing for power to beextracted) in the event that communication is lost between the phasecontrol system and a central controller or position measurement system.

In some embodiments, phase controller 802 is configured to provide acontrol signal to power electronics 804. Power electronics 804 isconfigured to electrically couple to the phase leads of the phase andprovide the current to the phase. Accordingly, power electronics 804includes components configured to operate at amperages and voltagesrelevant to the DC bus and phase leads. For example, power electronics804 may IGBTs, MOSFETs, busbars, shunts, sensors (e.g., for measuringcurrent or voltage), capacitors, diodes, any other suitable components,or any suitable combination thereof. Phase controller 802 need not beconfigured to electrically manage or interact with such large currentsor voltages as required by the phase leads and power electronics 804.For example, phase controller 802 may operate using relatively low DCvoltages (e.g., 5 VDC, 12 VDC, 24 VDC, 48 VDC) and provide low-voltagecontrol signals to power electronics 804 to control phase currents andvoltages. In some embodiments, phase controller 802 and powerelectronics 804 may be combined or integrated into a single moduleconfigured to control and apply current to the phase. In someembodiments, power electronics 804 may be shared among more than onephase. For example, power electronics 804 may include multiple powercircuits, be configured to receive multiple control signals, and beconfigured to apply current to more than one phase.

In some embodiments, the inclusion of brake resistor 806 in phasecontrol system 800 allows smaller, and possibly cheaper, brake resistorsto be used. For example, several small brake resistors and correspondingtransistors, distributed among phase control systems, are possiblycheaper than a single larger brake resistor and corresponding largecontactor. Further, the chance of complete failure of the brake resistorsystem is reduced. For example, if thirty phase control systems eachhave a brake resistor, in the event that one of the brake resistorsfails, there still exists 29/30 brake resistors for energy dissipation(e.g., for use during braking). This is advantageous compared to 0/30brake resistors of energy dissipation for the failure case of a singlebrake resistor for an entire LEM. In some embodiments, brake resistor806 is used in response to emergency situations (e.g., failures such asthe loss of grid-tie inverter 810) to sink power and decelerate motionof a translator. In some embodiments, brake resistor 806 (e.g., alongwith a corresponding transistor for switching) can be used to reducepower quickly for transient operation of the LEM (e.g., fastload-drops). For example, under some circumstances, in which there islimited DC bus capacitance, distributed brake resistors, controlled bytransistors rather than contactors, provide better control of the DC busvoltage than if a single brake resistor was used for an entire LEM.Brake resistor 806 may have any suitable resistance and be configuredfor any suitable power dissipation (e.g., the square of currentmultiplied by resistance). For example, brake resistor 806 may beconfigured to dissipate sufficient energy during a cycle of afree-piston generator to allow for a safe shutdown (e.g., slowing andstopping motion of a translator over the course of some number ofcycles).

In some embodiments, phase control system 800 may include power-outputleveler 808 to achieve a steadier power output on the DC bus. Forexample, power output levelers, also referred to as DC-DC converters,are further described in commonly assigned U.S. patent applicationtitled “DC-DC CONVERTER IN A NON-STEADY SYSTEM,” having Attorney DocketNo. 000102-0023-101, filed on Sep. 20, 2018, which is herebyincorporated by reference herein in its entirety. For example, afree-piston generator may output a pulsed power profile, and accordinglymay benefit from power-output leveler 808 providing a steadier poweroutput to grid-tie inverter 810. In an illustrative example, due to thereciprocating nature of a LEM, the LEM may exhibit a power fluctuationin time approximately twice the nominal power output of power-outputleveler 808. For example, this fluctuation could occur between nominalpower outputs of 250 to 500 kW. In some embodiments, power-outputleveler 808 includes significant capacitance, or a DC-DC bidirectionalconverter and some capacitance. In some such embodiments, thecapacitance, DC-DC bidirectional converter, or both, can be distributedto each phase control system corresponding to a LEM. For example, insome embodiments, a capacitor bank, DC-DC converter, or both may be ableto use one or more phase-current control transistors (e.g., of a systemsimilar to phase control system 800).

In some embodiments, a DC bus itself can be used to store and releaseelectrical energy, provided that power electronics 804 can tolerate avarying bus voltage. The use of the DC bus to store energy may beachieved by grid-tie inverter 810, for example, in accordance with thepresent disclosure.

Grid-tie inverter 810 is configured to manage electrical interactionsbetween an AC grid and a DC bus. In some embodiments, each phase controlsystem includes a grid-tie inverter and is configured to output, forexample, three-phase 480 VAC power. For example, some such embodimentsprevent the need for a distributed DC bus and allow use of cheaper andsafer distributed AC power. For example, in some embodiments, phasecontrol system 800 includes transistors configured to convert a local DCbus (i.e., for the phase) directly to 480 VAC 3 phase for gridinterconnection, rather than sharing a common DC bus with one or moreother phases. Accordingly, a DC bus may be, but need not be, sharedamong phases. In some embodiments, several phases, which need not becontiguous, or phases from two or more different LEMs, may share acommon DC bus to enable more constant AC power output, for example.

In some embodiments, power electronics 804 and power-output leveler 808are coupled to a DC bus managed by grid-tie inverter 810. In someembodiments, any of power electronics 804, power-output leveler 808, andgrid-tie inverter 810 may be combined or integrated. In someembodiments, phase control system 800 includes a connection to a batterybank and battery management system. For example, in someimplementations, a battery may be necessary to provide electrical energystorage. Each phase control system may include a connection to a batterybank, as well as a connection to a DC-DC converter. In some embodiments,phase control system 800 includes a battery bank and battery managementsystem (e.g., integrated into power electronics 804 or power-outputleveler 808). For example, each phase control system may include arelatively small battery rather than be coupled to a relatively largerbattery shared among DC buses of multiple phases (e.g., which representsa single point of failure).

Position estimator 812 is configured to estimate a relative position, anabsolute position, or both of a translator (e.g., a position of a faceof a piston or some other suitable reference) or section thereof (e.g.,a position of a magnet or pole thereof, or some other suitablereference). Position estimator 812 may estimate a position based on, forexample, a measured current, a calculated current, a measured voltage, acalculated voltage, a measured electromagnetic flux in a phase, acalculated electromagnetic flux in a phase, a measured position of amoving component (e.g., using an encoder tape and suitable encoderread-head), any other suitable information or any combination thereof.

In some embodiments, each phase control system may estimate position(e.g., include position estimator 812), rather than a central algorithmestimating or measuring position. Accordingly, the central algorithm maybe distributed among several phase control systems.

In some embodiments, each position estimator (e.g., each similar toposition estimator 812) for multiple phase control systems (e.g., eachsimilar to position control system 800) may participate in a distributedposition estimator. The distributed position estimator may estimateposition based on, for example, the sensing of phase voltage in eachcorresponding phase. In some such embodiments, a dedicated positionsensor need not be included, thus saving the cost and reliabilityconcerns of the position sensor.

Power supply 814 is configured to power components of phase controlsystem 800, aside from applying current to the corresponding phase. Forexample, power supply 814 may provide power for processing functions ofphase controller 802 or position estimator 812, diagnostics (e.g., forpower electronics 804, power-output leveler 808, grid-tie inverter 810,and position estimator 812), power switching on/off for brake resistor806, any other suitable process requiring power, or any suitablecombination thereof. In some embodiments, each phase control system mayinclude a power supply (e.g., similar to power supply 814). In manyinstances, a single power supply serving many components is a distinctfailure mode. For example, if every phase controller for multiple phasesis powered by a single power supply, the loss of the power supply wouldmean the loss in power for all the phase controllers. Accordingly, insome embodiments, each phase control system may include a DC powersupply. In some embodiments, a limited number of phase control systems(e.g., between 1 and N non-inclusively, and not necessarilycorresponding to contiguous phases) may be powered by a DC power supply.

In some embodiments, suitable components of phase control system 800 maybe coupled to a grid via coupling 850. For example, power-output leveler808, power electronics 804, grid-tie inverter 810, or a combinationthereof may be coupled to coupling 850. In some embodiments, coupling850 may include cables or buses transmitting AC power (e.g., three-phase480 VAC). In some embodiments, coupling 850 may include cables or busestransmitting DC power (e.g., a DC bus), which may be coupled to a gridvia a grid-tie inverter separate from phase control system 800, forexample. In some embodiments, grid-tie inverter 810 need not be includedin phase control system 800. For example, in some embodiments, coupling850 couples phase control system 800 to a DC grid, DC load, or othersuitable DC electrical architecture.

In some embodiments, suitable components of phase control system 800 maybe coupled to an energy storage device, DC-DC converter, or both, viacoupling 852. For example, power-output leveler 808, power electronics804, grid-tie inverter 810, or a combination thereof may be coupled tocoupling 852. In some embodiments, coupling 852 may include cables orbuses transmitting AC power (e.g., three-phase 480 VAC). In someembodiments, coupling 850 may include cables or buses transmitting DCpower (e.g., a DC bus). In some embodiments, coupling 850 and 852 may becombined (e.g., when an energy storage device and DC-DC converter arecoupled to a DC bus).

In some embodiments, suitable components of phase control system 800 maybe coupled to phases of a LEM via phase leads 854. For example, powerelectronics 804, brake resistor 806, or both, may be coupled to phaseleads 854. In some embodiments, phase leads 854 may include two phaseleads per phase corresponding to phase control system 800 (e.g., sixphase leads of three phases correspond to phase control system 800). Insome embodiments, phase leads 854 may include one phase lead per phasecorresponding to phase control system 800 (e.g., six phase leads of sixwye-connected phases correspond to phase control system 800).

In some embodiments, suitable components of phase control system 800 maybe coupled to communications (COMM) link 856. For example, phasecontroller 802, power electronics 804, power-output leveler 808,grid-tie inverter 810, position estimator 812, or a combination thereofmay be coupled to COMM link 856. In some embodiments, COMM link 856 mayinclude a wired communications link such as, for example, an ethernetcable, a serial cable, any other suitable wired link, or any combinationthereof. For example, in some embodiments, COMM link 856 includesmultiple cables, each corresponding to a port of a component of phasecontrol system 800. In some embodiments, COMM link 856 may include awireless communications link such as, for example, a WiFitransmitter/receiver, a Bluetooth transmitter/receiver, any othersuitable wireless link, or any combination thereof. COMM link 856 mayinclude any suitable communication link enabling transmission of data,messages, signals, information, or a combination thereof. In someembodiments, phase control system 800 is coupled to a central controlsystem via communications link 856. For example, in some embodiments,phase controller 802 communicates with a central controller via COMMlink 856.

Illustrative arrangements 400-700 of FIGS. 4-7 and phase control system800 of FIG. 8 may be used in accordance with the present disclosure tomanage electric power interactions between an AC grid and one or moreLEMs.

In some embodiments, the distribution of electronics increasesrobustness and overall system reliability.

In some embodiments, the use of more, smaller components allows volumecosts to be available. For example, if 120 power blades are used for alinear generator system having two LEMs, then 10,000# unit pricing isachieved at the construction of 100 linear generator systems.

In some embodiments, one or more components of a phase control systemhave a reduced power rating (e.g., in terms of current, voltage, orboth), which may allow for the use of smaller semiconductors. Inaddition to cost advantages and potential efficiency benefits, the useof smaller semiconductors also provides the possibility to increaseswitching frequency (e.g., generally lower caliber semiconductors arefaster). Further, reactive elements (e.g., capacitive andelectromagnetic components) are able to decrease in size as switchingfrequency increases. For example, regarding the arrangements of FIGS.4-7, separately controlling each phase directly allows the use ofdifferent topologies, in which reactive elements are included in thephase control system. This may improve the performance, cost, or both ofeach phase control system. Additionally, the use of phase controlsystems to control each phase may provide smoother voltage waveformsacross the phases, which would in turn reduce losses in the LEM.Further, the phase control system topology may provide voltage step-upfunctionality. For example, considering a system where the voltageacross a DC bus varies in time, this allows the design of a LEM with ahigher back-EMF. This is due to the removal of the constraint of a lowbus voltage configuration. The use of a higher DC bus voltagecorresponds to lower bus current, which reduces electrical losses (e.g.,ohmic losses). In an illustrative example, the voltage required across aphase to achieve a target current is primarily based on back emf andinductance. The back emf is related to force production from current(e.g., the larger the back emf, the larger the force per unit current).In a further illustrative example, a larger DC bus voltage may allow ahigher turn count in a phase winding (e.g., resulting in a larger backemf), which may allow for the use of switches having a smaller currentcapacity (e.g., smaller and cheaper switches).

In some embodiments, an increase in switching frequency provides ahigher bandwidth for control purposes. For example, a higher switchingfrequency may be used to maintain a desired controllability of a phasecontroller, while reducing the number of required sensors, thus reducingcosts and possibly improving reliability. To illustrate, a singlefeedback loop on phase current may be used in lieu of a two-statefeedback loop (e.g., phase voltage and phase current, or current andmode control).

In some embodiments, phase leads may be wired in a star configuration.For example, for a wye-type configuration, one phase lead from eachphase may be coupled together to form a neutral (e.g., having net zerocurrent input or output, so phase currents must sum to zero), while eachphase control system applies a controlled phase voltage, and thuscurrent, to the other lead of the corresponding phase. In some suchembodiments, only some of the DC bus voltage (e.g., the differencebetween a bus and the neutral voltage) may be available to apply acrosseach phase. In some embodiments, one or more subsets of phase leads maybe coupled in respective star configurations, having respective neutrals(e.g., that may be but need not be coupled together).

In some embodiments, phase leads for each phase may be wired in anindependent configuration. For example, a phase control system mayinclude a full H-bridge per phase and may be able to apply the full DCbus voltage across the phase in either direction (e.g., to cause adesired current to flow in either direction). This provides a largervoltage range available to each phase as well as complete controlindependence from the other phases. For example, without a commonneutral wye connection, the phase currents need not sum to zero.

In some embodiments, for which the phases are wired to correspondingphase control systems in an independent configuration, phase controlsystems may be interconnected in any suitable fashion (e.g., series,parallel, or a combination thereof). For example, each phase controlsystem may be provided power at a lower voltage than the DC bus voltage.This flexibility may aid in optimizing the overall cost and efficiencyof the system.

In some embodiments, a phase control system detects failures such asopens or shorts, and accordingly shuts itself off (e.g., does not applycurrent to the corresponding phase) to protect the rest of the system.Although a LEM will experience a reduction in overall power capabilityif a phase of the LEM is lost, the other phase control systems maycontinue operating. Accordingly, the LEM and distribution of phasecontrol systems may be configured to tolerate the loss of a phase. Forexample, if there exist planned service intervals for the overallsystem, a failed phase control system, or component thereof, could bereplaced at that time rather than as an emergency repair, and the lineargenerator could keep operating until that time (e.g., albeit at possiblyreduced power output).

In some embodiments, each phase control system may be configured toextract power from the corresponding LEM or LEMs. For example, in theevent of a detected system failure or a loss of communication with acontrol system, a part thereof, or other phase control system, a phasecontroller may attempt to extract energy from kinetic energy of atranslator by commanding current in the opposite direction of a back emfvoltage in the corresponding phase (e.g., use the phase to brake thetranslator motion).

In some embodiments, which include a long stator and short magnetsection (e.g., the phases extend spatially beyond a magnet section), forexample, some phases are unused for at least some of the magnet travel.For example, when no magnet is under a phase (e.g., not axiallyoverlapping with at least some of the phase), the phase will notinteract electromagnetically with the magnet section in a significantway. At a particular time during a stroke, unused phases may be used asinductors and the phase control system may be configured to store energyin capacitors or perform power conversion to help regulate the DC busvoltage, bus current, bus power, or a combination thereof. Accordingly,a phase control system, or phase controller thereof, may be used forother purposes besides exciting an electromagnetic force in the LEM.

FIG. 9 shows a flowchart of illustrative process 900 for managing phasecurrent (i.e., current in a phase), in accordance with some embodimentsof the present disclosure. For example, phase controller 802 of FIG. 8,or any of the phase control systems of FIGS. 4-7, may be configured toimplement the steps of illustrative process 900. The followingdescription is included in the context of a phase control system but maybe implemented using any suitable control circuitry. It will beunderstood that illustrative process 900 may be, for example, performedby multiple phase control systems corresponding to multiple phases,simultaneously or sequentially. Although discussed in the context of alinear multiphase electromagnetic machine (e.g., a free-pistongenerator), process 900 may be applied to any suitable multiphaseelectromagnetic machine.

Step 902 includes a phase control system detecting an event. An eventmay include, for example, a sample time of a processing algorithm,receipt of a signal (e.g., a message, value or flag), a failure toreceive a signal, a failure of a component, a feature in a measuredvoltage (e.g., an edge of a pulse), an analog signal, any other suitableevent, or any suitable combination thereof. For example, in someembodiments, a phase controller may detect a leading edge of a clocksignal (e.g., from a clock included in the phase controller, or from aclock signal communicated to the phase controller). In a furtherexample, a phase control system may receive an indication from a centralcontroller, the indication being the event. In some embodiments, forexample, the phase controller may execute an algorithm, and the eventmay be an indication to execute the current controller (e.g., as part ofa control scheme).

Step 904 includes a phase control system sensing the current in at leastone phase. In some embodiments, step 904 includes the phase controllerreceiving an input signal from a sensor configured to sense current inthe at least one phase corresponding to the phase controller. Forexample, a loop-type inductive sensor, or a voltage measurement across ahigh amperage precision resistor, may be used to provide a signal to thephase controller. In a further example, the phase controller may receiveinput from another system (e.g., a power electronics system) that mayinclude a current sensor. In some embodiments, the phase controller maysense one or more physical quantities and determine a current from thosequantities. For example, a phase controller may sense flux, phasevoltage, back emf, or other quantities, under suitable conditions, anddetermine current in the at least one phase based on its relation tothese sensed quantities. In an illustrative example, an analog currentsensor may be coupled to an analog-to-digital converter of the phasecontroller, which may sample the output of the current sensor at asuitable sampling rate. The sensor may be powered by a power supply ofthe phase control system, for example.

Step 906 includes a phase controller generating a control signal. Thephase controller may generate the control signal by executing analgorithm such as a feedback-loop control algorithm. In someembodiments, the phase controller determines a desired current value(e.g., in units of amps) and generates a control signal to communicatethe desired current value to a power electronics system. For example,the phase controller may generate a pulse-width modulation (PWM) signalto communicate to the power electronics system (e.g., which may activatean IGBT, MOSFET or other high-amperage switching component). In afurther example, the phase controller may communicate a messageindicative of a desired current using a user datagram protocol (UDP), atransmission control protocol (TCP), or other suitable protocol via anetwork connection to processing equipment included in a powerelectronics system. In a further example, the phase controller maygenerate a control signal indicative of a desired current using alow-voltage bus including any suitable number of conductors (e.g., viaCANbus, Modbus, SPI, or other serial bus or parallel bus). The controlsignal may include a digital signal, an analog signal, an opticalsignal, a message of any suitable format, any other suitable signal, anysuitable modulation thereof, or any suitable combination thereof.

Step 908 includes power electronics applying a phase current to the atleast one phase based in part on the control signal of step 906. In someembodiments, the power electronics includes one or more switchingcomponents configured to apply a commutated voltage to phase leads. Forexample, in some embodiments, the power electronics may include one ormore switches (e.g., IGBTs, MOSFETs, SiC-based MOSFETS, or othersuitable components), or any other suitable switching component,arranged in any suitable arrangement (e.g., H-bridge, star-connected),which can apply voltage from a DC bus to phase leads of the at least onephase for a predetermined schedule. To illustrate, the control signalmay include a PWM signal configured to open/close the switch, withsuitable commutation, for a period of time indicative of the duty cycleof the PWM signal (e.g., longer duty cycles correspond to larger phasecurrents as the switches are activated for a longer time). In a furtherexample, in some embodiments, the power electronics may include a halfbridge of switches, and the phase leads may be wye-connected, and thepower electronics can apply voltage from one bus of the DC bus to aphase lead of the at least one phase for a predetermined schedule.

In some embodiments, the phase controller uses desired currents in allphases of a LEM in generating a control signal. For example, consideringwye-connected phases, the currents for all of the phases connected tothe neutral must sum to zero (i.e., by Kirchhoff's current law asapplicable). Accordingly, all phase controllers corresponding to a LEMmay determine desired current values constrained to sum to zero.

It will be understood that in the context of FIG. 9, a desired currentvalue may be replaced by, or supplemented by, a desired phase voltage orany other value that may be indicative of a desired current. Forexample, a phase controller may determine a desired phase voltage, adesired PWM duty cycle, a desired commutation (e.g., positive ornegative current), or any other suitable value or combination of values.In a further example, the illustrative steps of process 900 may beimplemented during normal operation, braking, or both to manage one ormore phase currents.

FIG. 10 shows a flowchart of illustrative process 1000 for managing oneor more failed phase control systems, in accordance with someembodiments of the present disclosure. The steps of illustrative process1000 may be performed by a plurality of phase control systems, a centralcontroller, or a suitable combination thereof. The following descriptionwill reference control circuitry which may be included in any suitablecontroller or control system. In some embodiments, the illustrativesteps of process 1000 are performed in response to detecting an eventsuch as a fault (e.g., a short in a phase, a non-responsive phase, analtered property of a phase). Although discussed in the context of alinear multiphase electromagnetic machine (e.g., a free-pistongenerator), process 1000 may be applied to any suitable multiphaseelectromagnetic machine.

Step 1002 includes control circuitry determining if phase controlsystems, or components thereof, have failed. In some embodiments, eachphase control system may perform step 1002. For example, a plurality ofphase control systems may communicate with one another and indicate(e.g., using any suitable communication protocol) to other phase controlsystems if a local failure occurs (i.e., the instant phase controlsystem fails). To illustrate, each phase control system may send astatus indicator to all other phase control systems, which may beconfigured to indicate if a failure has occurred. Further, the absenceof an indication may also be used to determine that a failure hasoccurred. In some embodiments, a central control system may communicatewith each phase control system and determine if one has failed (e.g., bylack of communication, or an affirmative indication of failure). In someembodiments, a central control system, one or more phase controlsystems, or a combination thereof may determine that a phase controlsystem has failed based on measured or calculated values of operatingconditions of the LEM. For example, if a measured current, voltage,flux, back emf, other signal, or feature of a signal indicates a failureof a particular phase, the corresponding phase control system may bedetermined to have failed. In some embodiments, a failure of a phasesuch as a short, an open circuit, thermal degradation, or other failureevent may cause the determination that a phase control system hasfailed. In a further example, if a grid-tie inverter is determined tohave failed, the control circuitry may determine that any phase controlsystem coupled to the failed grid-tie inverter has also failed. Afailure event may include a failure of any component of a phase controlsystem (e.g., any of the components or systems of FIG. 8), a phaseitself (e.g., a winding of the phase, an interconnect of the phase, or aferrous core of the phase), a phase lead, a grid-tie inverter, a DC bus,a lead coupled to a DC bus, a DC-DC converter, a sensor, acommunications link, a component (e.g., an energy storage device), anyother suitable component or system, or any combination thereof.

If it is determined at step 1002 that no phase control systems havefailed, the phase control systems may proceed to execute or continueexecuting process 900 of FIG. 9. for example. If it is determined atstep 1002 that one or more phase control systems have failed, then thecontrol circuitry may proceed to step 1004. Step 1004 includes controlcircuitry identifying one or more phase control systems that havefailed. In some embodiments, step 1004 may be combined with step 1002.For example, the determination that at least one phase control systemhas failed may include identifying the phase control system. Step 1004may include control circuitry determining an address (e.g., an IPaddress or other communication address of a failed phase controlsystem), an index (e.g., an integer indicating which phase controlsystem has failed), a phase index (e.g., phase j of a LEM), a serialnumber, any other suitable identification, or any combination thereof.

Step 1006 includes control circuitry isolating the at least one failedphase control system. In some embodiments, step 1006 includes a phasecontroller generating a control signal indicative of zero current (e.g.,a PWM signal with a minimal duty cycle). In some embodiments, step 1006includes a phase controller ceasing to generate any control signal(e.g., ceasing communication with power electronics). In someembodiments, step 1006 may include one or more switching components(e.g., a contactor, a transistor, or a relay) to open a circuit, therebypreventing application of a DC bus voltage to a phase lead coupled tothe failed phase control system. Step 1006 includes an electricalisolation, thereby preventing current from being applied by a failedphase control system, current being applied to a failed phase, or both.

Step 1008 includes control circuitry modifying one or more currentconstraints for non-failed (e.g., still operable) phase control systems.For example, if one or more phase control systems fail, the remainingphase control systems may allow continued operation of the correspondingLEM(s). However, if not all phase control systems are able to applycurrent to corresponding phases (e.g., isolated phase control systemsfrom step 1006), the amount of current applied by the remaining phasecontrol systems may be modified. For example, to achieve the sameelectromagnetic force with some phases disabled requires increasedcurrent flow in the remaining phases, with the current distributionamong phases being determined using any suitable method. In anillustrative example, considering wye-connected phases, the isolation ofa phase control system and corresponding one or more phases requires theapplied current in the remaining phases to sum to zero. In someembodiments, the determination of current by either a central controlsystem, a phase controller, or both, may be modified to reflect theisolation of one or more phase control systems. For example, in someembodiments, following identification and isolation of a failed phasecontrol system, the remaining phase control systems may perform process900, based only on the remaining phase control systems (e.g., allottingno current to phases corresponding to a failure). Each time a failureevent is detected, the determination of current may be furtherconstrained to reflect the isolation of the corresponding phase controlsystem. Further, it may be determined at step 1008 that the LEM shouldstop operating (e.g., begin auto-braking). For example, if a sufficientnumber of phases corresponding to failed phase control systems cannothave current applied due to isolation (e.g., at step 1006), the controlcircuitry may determine that continued operation is unsafe, inefficient,or otherwise undesirable, and accordingly manage shutdown of the LEM(e.g., including slowing and stopping motion of a correspondingtranslator). A sufficient number of phases may be determined by theinability of a desired electromagnetic force to be achieved, a desiredtranslator position to be reached, or otherwise the inability of aproperty of the system to achieve a desired value.

It is contemplated that the steps or descriptions of FIGS. 9-10 may beused with any other embodiments of the present disclosure. In addition,the steps and descriptions described in relation to FIGS. 9-10 may bedone in alternative orders or in parallel to further the purposes ofthis disclosure. Further, each of these steps may be performed in anyorder or in parallel or substantially simultaneously to reduce lag orincrease the speed of the system or method. Any of these steps may alsobe suitably skipped or omitted from the process. Furthermore, it shouldbe noted that any of the suitable devices or equipment discussed inrelation to FIGS. 1-8 could be used, alone or in concert, to perform oneor more of the steps in FIGS. 9-10.

Any of the illustrative processes and systems of FIGS. 11-31, describedin the context of braking, may be applied to one phase of anelectromagnetic machine, more than one phase of an electromagneticmachine, phases of more than one electromagnetic machine (e.g., statorsassociated with opposing translators), or any combination thereof.Further, the braking techniques may be applied to electromagneticmachines having one phase or more than one phase. Any of theillustrative techniques, systems, and configurations shown in FIGS. 1-10may be used to implement any of the braking processes of the presentdisclosure.

In some embodiments, the control system may detect an event duringoperation and determine an electromagnetic technique to brake thetranslator(s) to shut down, slow down, or stop moving over a suitabletime period. FIG. 11 shows a flowchart of illustrative process 1100 forauto-braking, in accordance with some embodiments of the presentdisclosure. The steps of illustrative process 1100 may be performed byone or more phase control systems, a central controller, or a suitablecombination thereof. The following description will reference controlcircuitry which may be included in any suitable controller or controlsystem.

Measurements 1101 may include sensor signals, metrics derived fromsensor signals, an output of a model (e.g., output of an observer orestimation of a physical quantity or operating parameter), any othersuitable value or metric indicative of an operating parameter, or anycombination thereof. Step 1102 includes the control circuitry detectingan event, or otherwise determining an event has occurred. In someembodiments, the event may include a fault event or a failure event.Depending upon whether the control circuitry has detected an event atstep 1102, the control circuitry may proceed to either braking process1106 or normal operation 1104. Normal operation 1104 is an illustrativeprocess performed when no event has been detected. Braking process 1106is an illustrative process performed in response to an event beingdetected (e.g., a fault requiring auto-braking). In some embodiments,control circuitry may determine a type of fault, availabilityinformation for one or more operating parameters (e.g., what, if any,information is available in regards to an operating parameter), a lossin communication, any other suitable fault, or any combination thereof.In an illustrate example, a control system may repeatedly perform step1102 to check for faults and perform step 1104 until a fault isdetected. Step 1106 may include modifying an algorithm for determiningphase currents, changing a constraint on phase currents, determiningdesired position information associated with braking (e.g., reducedstroke length and reduced translator velocities), determining desiredforce information associated with braking (e.g., a desired braking forceapplied to a translator, a synchronized braking force applied to morethan one translator), any other suitable modification, or anycombination thereof. In some embodiments, the control circuitry maydetermine the braking algorithm based on the type of fault. For example,if position information is available and current information isavailable, the control circuitry may continue to determine phasecurrents as during normal operation while adjusting desired targetpositions to slow the translators. In a further example, if positioninformation is unavailable, the control circuitry may perform a positionestimation or emf polarity estimation to determine phase currents.

In some embodiments, process 1100 may be implemented by more than onecontroller or control system. For example, during normal operation(e.g., step 1104) a first controller may be used, and during braking(e.g., step 1106) a second controller may be used. In some embodiments,a controller activated for braking may be relatively simpler (e.g., lesscomputationally complex) than a controller used for normal operation.Because braking may involve operating conditions that are not requiredto be efficient, precise, or include very tight tolerances in operationparameter values, the associated controller or control system mayinclude relatively fewer parameters, relatively fewer commands, orotherwise be configured to operate more simply. In some embodiments, acontroller used during braking may have an associated power supply, anassociated communications link, an associated processor, any otherassociated or dedicated equipment, or any combination thereof. In someembodiments, separate control systems for normal operation and brakingprovide redundancy. For example, in the event of a failure of the normaloperation control system, the braking control system may remainfunctional and capable of braking one or more translators. In someembodiments, one braking controller, or more than one braking controllermay be included. For example, each phase, motor, or other suitable groupof hardware may have an associated respective braking controller.

In some embodiments, process 1100 may include more than one controlalgorithm, implemented by a single control system. For example, duringnormal operation (e.g., step 1104) a first algorithm may be used, andduring braking (e.g., step 1106) a second algorithm may be used. In someembodiments, the control system may implement a flag, state machine(e.g., configured to manage system states), or other suitable managementmechanism for managing algorithm states.

FIG. 12 shows illustrative arrangement 1200, including power electronicssystem 1230 coupled to phase 1240 of a multiphase electromagneticmachine, in accordance with some embodiments of the present disclosure.Arrangement 1200 includes motor controller 1260, sensor 1250,differentiator 1260, and comparator 1270, which may be configured tocontrol a current in phase 1240 (e.g., of multiphase electromagneticmachine 1297 which is not explicitly shown in FIG. 12). In someembodiments, sensor 1250 may include a current sensor, anddifferentiator 1280 and comparator 1270 may be used to determine a signof a derivative of a sensed current.

In some embodiments, differentiator 1280, comparator 1270, or both, areimplanted in hardware. For example, differentiator 1280 may beimplemented using analog circuitry including an operational amplifier,capacitors, and resistors. Further, comparator 1270 may be implementedusing analog circuitry including an operational amplifier. Accordingly,for example, a signal from sensor 1250 may be differentiated bydifferentiator 1280, and then compared with Vref 1274 (e.g., which maybe zero volts) to determine a sign of the differentiated value. Toillustrate, if the differentiated signal is greater than Vref 1274, thencomparator 1270 may output a digital high (e.g., a “one” in binary), andconversely if the differentiated signal is less than Vref 1274, thencomparator 1270 may output a digital low (e.g., a “zero” in binary). Insome embodiments, Vref 1274 may be provided by motor controller 1260. Insome embodiments, Vref 1274 may be a ground (e.g., chassis). Vref 1274may include any suitable reference voltage.

In some embodiments, differentiator 1280, comparator 1270, or both, areimplemented in software (e.g., of motor controller 1260). For example, asignal from sensor 1250, which may be indicative of instantaneouscurrent in phase lead 1242, may be received at motor controller 1260.Motor controller 1260 may process the signal, apply one or moremathematical operations, apply one or more signal operations, or acombination thereof, to determine a value indicative of a derivative ofthe signal, and then compare the value to a reference value. In someembodiments, motor controller 1260 may store historical values, and mayestimate a sign of a derivative based on a weighted combination ofhistorical values. For example, any suitable numerical technique may beused to estimate a sign of a derivative of a measured current, inaccordance with the present disclosure.

Sensor 1250 may include any suitable sensor for sensing an electricalparameter of phase lead 1242. As shown in FIG. 12, sensor 1250 mayinclude a loop current sensor, which may be configured to output asignal indicative of instantaneous current in phase lead 1242. However,any suitable sensor may be used in accordance with the presentdisclosure. For example, sensor 1250 may include a voltage sensor,configured to measure a phase voltage between phase leads 1242 and 1244,either phase lead 1242 or 1244 and a ground, or any combination thereof.

In some embodiments, one or more components of arrangement 1200 may begrouped, integrated, or otherwise combined. For example, system 1290shows an illustrative grouping including motor controller 1260,comparator 1270, and differentiator 1280, which may be implemented as anintegrated system (e.g., in hardware or software). To illustrate, insome embodiments, control system 350 of FIG. 3 includes system 1290. Ina further example, system 1295 shows an illustrative grouping includingpower electronics system 1230, sensor 1250, and phase leads 1242 and1244, which may be implemented as an integrated system, coupled tomultiphase electromagnetic machine 1297 via interconnects 1298. Toillustrate, in some embodiments, power electronics system 330 of FIG. 3includes system 1295 (e.g., and accordingly, sensor 1250 may be coupledto power electronics system 1230). It will be understood that systems1290 and 1295 are illustrative, and that any suitable grouping orintegration may be used, in accordance with the present disclosure. Insome embodiments, system 1290 need not be included, and sensor 1250 iscoupled to power electronic system 1230, a control system, a subsystemor module, or a combination thereof.

Equation 1, below, provides an illustrative example of how phase voltageV for phase j (i.e., the voltage drop across phase j, measured acrossphase leads 1242 and 1244 at power electronics system 1230), current ifor phase j (e.g., as measured by sensor 1250), resistance R in phase j,inductance L in phase j (e.g., the inductance of windings of phase 1297,which may depend on position, flux, current, and/or other parameters),the time derivative of current i in phase j, force constant k in phase j(e.g., which may depend on position, flux, current, and otherparameters), and translator velocity (e.g., the translator thatinteracts electromagnetically with phase j) are related, when the phaseis not being shorted.

$\begin{matrix}{V_{{Phase},j} = {{i_{j}R_{j}} + {L_{j}\frac{{di}_{j}}{dt}} + {k_{j}v}}} & {{Equation}\mspace{14mu} 1}\end{matrix}$

The first term on the right hand side (RHS) of Equation 1 representsohmic voltage drop in phase j, the second term on the RHS representsinductive voltage drop in phase j, and the third term on the RHSrepresents the back emf (e.g., from motion of the translator).

Equation 2 provides an illustrative example of how back emf for phase j(e.g., phase 1297), inductance L in phase j, and the time derivative ofcurrent i in phase j, are approximately related, when the phase is beingshorted (e.g., phase leads 1242 and 1244 connected together at powerelectronics system 1230). Note that Equation 2 can be arrived at fromEquation 1 by defining V_(phase,j) as zero (e.g., the phase leads areshorted), and neglecting the ohmic voltage drop term.

$\begin{matrix}{0 \sim {{L_{j}\frac{{di}_{j}}{dt}} + {k_{j}v\mspace{14mu} {or}}}} & {{Equation}\mspace{14mu} 2} \\{{{- L_{j}}\frac{{di}_{j}}{dt}} \sim {{back}\mspace{14mu} {emf}}} & {{Equation}\mspace{14mu} 3}\end{matrix}$

Equation 3 results from algebraically rearranging Equation 2, wherek_(j)*v is back emf. Equation 3 shows that the sign of the back emf maybe approximated from the sign of the derivative in current (e.g., theyhave opposite sign in Equation 3).

Equation 4, below, provides an illustrative example of how phase voltageV for phase j (i.e., the voltage drop across phase j) and back emf arerelated, when phase j has no current (e.g., phase leads 1242 and 1244are not connected to each other or a bus at power electronics system1230). For example, Equation 4a may be relevant when the powerelectronics system attempts to apply a current of zero, or ifcorresponding switches (e.g., which couple the phase leads to buses orneutrals) are not activated at all. In a further example, Equation 4bmay be relevant when the power electronics system attempts to apply a DCcurrent (e.g., which simplifies to Equation 4a if the resistance R issmall).

V _(Phase,j) ˜k _(j) v=back emf  Equation 4a:

V _(Phase,j) =R*1+back emf  Equation 4b:

In some embodiments, a controller may be configured to determine acontrol signal based on a polarity indicative of emf. FIG. 13 showsillustrative controller 1300 for determining control signal 1350, inaccordance with some embodiments of the present disclosure. Controller1300 may be implemented in any suitable hardware, software, orcombination thereof. Controller 1300 will be described below in terms ofphase j, wherein control signal 1350 may be configured to direct powerelectronics to apply current to phase j. In some embodiments, theactions performed by controller 1300 may be multiplexed (e.g., a vectorof values are passed along the modules, and control signal 1350 is amultiplexed signal). In some embodiments, a set of controllers similarto controller 1300 are included and each may output a control signal torespective power electronics to apply current to a respective phase. Inan illustrative example, controller 1300 may be implemented in real timeon processing equipment such as control system 350, shown in FIG. 3. Thefollowing discussion with respect to FIG. 13 will be in terms ofsequential logic and operations, for simplicity, but may be implementedusing any suitable computational arrangement. In some embodiments,controller 1300 is configured for braking a translator by applying abraking current (e.g., a phase current causing an electromagnetic forceon a translator opposing motion of the translator).

Measured current 1304 may be received from any suitable hardware orsoftware. For example, a signal from a current sensor may be provided toan analog-to-digital converter of a control system that may providemeasured current 1304 at a fixed sampling frequency.

Shorting waveform 1302 may be configured to output, for example, abinary signal defining when a phase is to be shorted in time. Forexample, waveform 1301 includes high values (e.g., shorting), and lowvalues (e.g., not shorting), indicating a schedule for shorting phase j.

Inverter 1306 may be configured to invert the output of shortingwaveform 1302. For example, when waveform 1301 is high, inverter 1306may output low, and when waveform 1301 is low, inverter 1306 may outputhigh.

Current latch 1308 may output a latest measured current 1304 value whenthe output of inverter 1306 is high, and may output a fixed value (e.g.,the last value) when the output of inverter 1306 is low.

Current difference latch 1310 (i.e., latch 1310) may be configured tooutput a latest difference between measured current 1304 and the latchedoutput of latch 1308 when the output of shorting waveform 1302 is high,and may output a fixed value (e.g., the last value) when the output ofshorting waveform 1302 is low.

Maximum current 1312 may be configured to include a constant value(e.g., 350 amps), a varying value (e.g., dependent upon otherparameters), or any other suitable value of a maximum desired current.For example, maximum current 1312 may include a maximum safe currentvalue to be applied to phase j during braking with respect tocapabilities of power electronics, a multiphase electromagnetic machine,or both.

Sign 1314 may be configured to output either a positive or negativereference value based on the sign of input. For example, if the outputof latch 1310 is positive, sign 1314 may output a positive one, while ifthe output of latch 1310 is negative, sign 1314 may output a negativeone. Accordingly, sign 1314 may be used to normalize the output of latch1310, while preserving the sign (e.g., or preserving the opposite of thesign, if sign 1314 is inverted).

Multiplier 1316 may be configured to multiply the output of maximumcurrent 1312 and sign 1314 to generate a maximum current of a desiredsign, for braking.

Addition 1318 may be configured to combine the output of multiplier 1316and measured current 1318 to generate an error, or difference, signal.The error signal may be indicative of how different the measured currentis from the desired maximum current. As shown in FIG. 13, addition 1318combines the output of multiplier 1316 with the negative of measuredcurrent 1304 (i.e., subtracts measured current from the output ofmultiplier 1316).

Gain 1320 may be configured to multiply the output of addition 1318 by afactor, which may be constant or may depend on other parameters. Forexample, gain 1320 may multiply the output of addition 1318 by aconstant indicative of P-control (e.g., a proportional controller).

Saturation 1322 may be configured to limit the output of gain 1320before multiplier 1324. For example, saturation 1322 may limit theoutput of gain 1320 to values between a predetermined maximum value anda predetermined minimum value. Saturation 1322 may be configured toprevent ill-defined, dangerous, or non-sensical values from propagatingto multiplier 1324.

Multiplier 1324 may be configured to multiply the output of saturation1322 by the output of inverter 1306. Accordingly, if shorting waveform1302 outputs a high (e.g., shorting), then multiplier 1324 outputs zero(i.e., zero multiplied by the output of saturation 1322 is zero), and nocontrol signal is outputted when shorting (e.g., control signal 1350 isinactive). Also, if shorting waveform 1302 output a low (e.g., notshorting), then multiplier 1324 outputs the output of saturation 1322,and control signal 1350 is active when not shorting (e.g., when phasecurrent may be desired).

Control signal 1350 may be outputted to, for example, power electronics,to cause the application of current in phase j. In an illustrativeexample, control signal 1350 may include a PWM signal, with acorresponding duty cycle that specifies an “on” time for a switch (e.g.,an IGBT, a MOSFET or any other suitable device). In some embodiments,control signal 1350 may include more than one signal for causing theapplication of current to phase j. For example, for wye connectedphases, control signal 1350 may include signals for connecting a phaselead to a high bus or a low bus of a DC bus (e.g., using a set of IGBTs,MOSFETs or other components).

When shorting waveform 1302 outputs a low value (e.g., not shorted),latch 1308 is active, and the value latched current (i.e., “ILAST” asthe output of latch 1308) is updated at latch 1310. However, latch 1310is not active, and outputs a fixed (i.e., latched) value. The output ofinverter 1306 is high, and accordingly, control signal 1350 is active,outputting a control signal indicative of maximum current 1312, having adesired sign. Note that as shown in FIG. 13, sign 1314 does not changevalue when latch 1310 is not active.

When shorting waveform 1302 output a high value (e.g., shorted), latch1308 is inactive, the latched current (i.e., output of latch 1308) isnot updated at latch 1310. However, when latch 1310 is active, itoutputs a difference between a measured current 1304 and latched currentfrom before latch 1308 was inactive (i.e., the difference is beingupdated). The output of inverter 1306 is low, and accordingly, controlsignal 1350 is inactive, and no control signal is outputted. Note thatas shown in FIG. 13, latched current does not change value when latch1308 is not active.

By alternating between a shorting and non-shorting state, controller1300 may apply a maximum desired current, having a desired sign, tobrake a translator of a multiphase electromagnetic machine. Whenshorting, controller 1300 updates information on the derivative ofmeasured current (e.g., and also back emf). When not shorting,controller 1300 causes the application of a maximum desired brakingcurrent having an appropriate sign.

FIG. 14 shows illustrative controller 1400 for processing output ofcontroller 1300 of FIG. 13, in accordance with some embodiments of thepresent disclosure. For discussion purposes, controller 1400 may providea simplified representation of a power electronics system and amultiphase electromagnetic machine. The description of controller 1400is intended to provide illustrative results of applying a control signalto power electronics to cause the application of current in a phase, tobrake a translator. Control signal 1408 may be similar to control signal1350 of FIG. 13 but need not be identical. The plots provided in FIGS.15-16 are illustrative of information that may be derived fromcontroller 1400 and controller 1300, for example, and may be indicativeof a multiphase electromagnetic machine, which may be approximatelymodeled by controller 1400.

Back emf 1420 may be estimated, for example, as the product oftranslator velocity 1402 and force constant 1404, as multiplied bymultiplier 1406.

Phase voltage 1430 is estimated as a proportionality factor multipliedby control signal 1408. For example, if control signal 1408 is a PWMsignal, phase voltage 1430 may be proportional to the PWM duty cycle(e.g., full duty cycle corresponds to full DC bus voltage, or busline-to-neutral phase voltage). As shown in FIG. 14, phase voltage“VPHASE” is determined from control signal 1408 at gain 1410.

Current 1422 in phase j (e.g., which may serve as an estimate ofmeasured current 1304 in FIG. 13) is determined based on a voltagesummation performed at addition 1414, division by inductance L at gain1416, and integral 1418 (e.g., which converts the time derivative ofcurrent to current 1422). Controller 1400 as illustrated in FIG. 14performs a computation similar to that represented by Equation 1,although solving for current 1422.

Instantaneous electrical power from phase I is given as the output ofmultiplier 1424, which multiplies instantaneous current 1422 and phasevoltage 1430. Cumulative energy 1428 is the time integral, viaintegrator 1426, of instantaneous power from a suitable starting point.

FIGS. 15-16 show illustrative output of controller 1400 of FIG. 14,using data and illustrative model values. It will be understood thatcontroller 2200 and 1400, as well as the plots shown in FIGS. 15-16, aremerely illustrative and are included to provide examples in accordancewith the present disclosure.

FIG. 15 shows a plot 1500 of an illustrative energy metric correspondingto a multiphase electromagnetic machine, in accordance with someembodiments of the present disclosure. The metric shown in plot 1500 iscumulative energy removed from a translator during braking. As shown,most of the energy is removed in about one time scale 1502 (i.e., a unitmeasure of time). Time scale 1502 may be any suitable time period,number of strokes, number of cycles, clock pulses, sampling points, orother progressing variable. In some embodiments, braking may occurrelatively quickly (e.g., within a stroke, or several strokes), and thebraking force may be relatively large (e.g., larger than electromagneticforces applied during normal operation). In some embodiments, brakingmay occur relatively slowly (e.g., over the course of many strokes), andthe braking forces may be relatively smaller (e.g., similar to orsmaller than electromagnetic forces applied during normal operation).

FIG. 16 shows plots 1610 and 1620 of illustrative signals correspondingto a phase of a multiphase electromagnetic machine, in accordance withsome embodiments of the present disclosure. Plot 1610 shows illustrativeshorting waveform 1611, for which the pulses correspond to shorting(e.g., shorting when high, not shorting when low). Plot 1620 showsillustrative phase current 1621 and emf 1622 corresponding to theshorting waveform. In some embodiments, the frequency of pulses ofshorting waveform 1611 is higher than the frequency of polarity changesof the phase current or emf.

FIG. 17 shows a flowchart of illustrative process 1700 for managingcurrent in one or more phases of a multiphase electromagnetic machine,in accordance with some embodiments of the present disclosure. Process1700 is an illustrative example of process 1100 of FIG. 11, includingnormal operation and a braking process.

Step 1702 includes the control circuitry detecting an event, orotherwise determining an event has occurred. In some embodiments, theevent may include a fault event or a failure event. For example, a faultevent may include a loss of communication in a control system (e.g.,control system 350 of FIG. 3). In a further example, a fault event mayinclude an unintended short of a phase in a multiphase electromagneticmachine (e.g., multiphase machine 340 of FIG. 3). In a further example,a fault event may include a loss in signal from a sensor as received bya control system (e.g., an encoder, a phase current sensor, or a DC busvoltage sensor). In a further example, a fault event may include a modechange to “stop” from a control system, during which braking is desired.In a further example, a fault event may include a loss of PWM control,or a PWM signal thereof, from a control system or phase control system.In a further example, a fault event may include a loss of a DC bus(e.g., loss of DC bus voltage), a loss in control of the DC bus, or aloss of a component coupled to the DC bus (e.g., an energy storagedevice). In some embodiments, control circuitry may determine an eventhas occurred by performing a set of diagnostics (e.g., checking thatsignals are refreshing, checking that sensors are providing signals,checking that all communications between systems and subsystems areoccurring).

Depending upon whether the control circuitry has detected an event atstep 1702, the control circuitry may proceed to either process 1750(e.g., step 1704) or process 1770 (e.g., step 1710). Process 1770 is anillustrative process performed when no event has been detected (e.g.,normal operation). Process 1750 is an illustrative process performed inresponse to an event being detected (e.g., a fault requiringauto-braking).

Step 1704 includes the control circuitry determining whether to shortphase j. In some embodiments, step 1704 is repeated for all phases of amultiphase electromagnetic machine. In some embodiments, controlcircuitry decides whether to short phase j based on a shorting waveform.For example, a shorting waveform may include a series of binary valuesand, depending on whether the values are 0 or 1, the control circuitrymay determine whether to short phase j or not.

Step 1706 includes the control circuitry causing a shorting process tooccur via a power electronics system. In some embodiments, the controlcircuitry transmits a control signal to the power electronics system toshort phase j. Step 1706 may include, for example, the control circuitrysending a control signal to the power electronics system for switchingsuitable contactors to short phase j, the control circuitry sending acontrol signal to the power electronics system for switching suitabletransistors to short phase j, performing a measurement indicative ofcurrent in phase j, performing a measurement indicative of voltage inphase j, performing a measurement indicative of magnetic flux in phaseI, or any suitable combination thereof. In some embodiments, the controlcircuitry maintains shorting process 1706 for a predetermined period oftime, before returning to step 1704. In some embodiments, the controlcircuitry may repeat steps 1704 and 1706 sequentially (e.g., in acontrol loop) until the control circuitry determines not to short phasej. The power electronics system is configured to receive the controlsignal, which may be in the form of a digital signal (e.g., a binaryzero or one, a PWM signal, a pulse signal), a message (e.g., a UDP orTCP message transmitted over ethernet), an analog signal (e.g., ananalog voltage or current signal), any other suitable signal, modulationthereof, or any combination thereof.

Step 1708 includes the control circuitry causing a braking process tooccur via the power electronics system. When the control circuitrydecides at step 1704 to not short phase j, a desired phase current maybe determined, and a control signal indicative of the desired phasecurrent may be transmitted to the power electronics system. In response,the power electronics system may apply a current to phase j, forexample, causing braking of a translator by applying an electromagneticforce on the translator in a direction opposite to the direction ofmotion of the translator. The braking process includes applying currentto a phase such that the product of current and phase voltage (e.g., orPWM command) is negative. The magnitude of the applied current can beany suitable value including, for example, a maximum absolute value, anominal value, a value determined in real time based on other operatingparameters. In an illustrative example, the magnitude of the current maybe determined as a maximum safe value in view of the power electronicssystem's capabilities, a maximum current rating of a component ormaterial, or a maximum current value to keep the resultingelectromagnetic force within a threshold.

In some embodiments, the time scale for performing step 1706 and step1708 is dependent on the time scale of any changes in sign of the backemf in the phase. For example, the loop of step 1704 to step 1706 tostep 1704 may be performed on a time scale much smaller than acharacteristic time for the back emf to switch sign in the phasewinding. Accordingly, this may help reduce the time during which step1708 is not occurring (e.g., no braking is occurring), while not riskingthe back emf polarity changing. Additionally, in some circumstances itis preferred to perform step 1708 for a relatively longer time than step1706 (e.g., to accomplish more braking), but not so long as a change insign of back emf occurs.

Step 1710 includes the control circuitry determining whether to shortphase j, under circumstances where no event has been detected. In someembodiments, step 1710 is repeated for all phases of a multiphaseelectromagnetic machine. In some embodiments, control circuitry decideswhether to short phase j based on a shorting waveform. For example, ashorting waveform may include a series of binary values and depending,on whether the values are 0 or 1, the control circuitry may determinewhether to short phase j or not. In some embodiments, the controlcircuitry performs step 1710 less frequently than step 1704 when anevent has been detected, because during normal operation it may not bepreferred to short the phase periodically. In some embodiments, thecontrol circuitry need not perform step 1710, and rather determines toshort phase j only when an event has been detected (e.g., at step 1704).

Step 1712 includes the control circuitry causing a shorting process tooccur via a power electronics system. In some embodiments, the controlcircuitry transmits a control signal to the power electronics system toshort phase j. Step 1712 may include, for example, the control circuitrysending a control signal to the power electronics system for switchingsuitable contactors to short phase j, the control circuitry sending acontrol signal to the power electronics system for switching suitabletransistors to short phase j, performing a measurement indicative ofcurrent in phase j, performing a measurement indicative of voltage inphase j, performing a measurement indicative of magnetic flux in phaseI, or any suitable combination thereof. In some embodiments, the controlcircuitry maintains shorting process 1712 for a predetermined period oftime, before returning to step 1704. In some embodiments, the controlcircuitry may repeat steps 1710 and 1712 sequentially (e.g., in acontrol loop) until the control circuitry determines not to short phasej. The power electronics system is configured to receive the controlsignal, which may be in the form of a digital signal (e.g., a binaryzero or one, a PWM signal, a pulse signal), a message (e.g., a UDP orTCP message transmitted over ethernet), an analog signal (e.g., ananalog voltage or current signal), any other suitable signal, modulationthereof, or any combination thereof.

Step 1714 includes the control circuitry determining a desired currentto be applied to phase j. The control circuitry may determine thedesired current for phase j using any suitable technique, in accordancewith the present disclosure. For example, the control circuitry maydetermine a desired current for phase j using any of techniquesdisclosed in commonly assigned U.S. Pat. No. 8,344,669 filed on Apr. 2,2012, which is hereby incorporated by reference herein in its entirety.In a further example, step 1714 may include the control circuitrydetermining a desired current to be applied to phase j based on sensorinput, a control scheme (e.g., feedback control using a PID controller),a mathematical model, a neural network, a lookup table (e.g., based ontranslator position and speed, as well as a tabulated force constant),any other suitable computation technique, or any suitable combinationthereof. Sensor input may include signals received from an encoder(e.g., an optical encoder, or a magnetic encoder), a piezoelectricsensor (e.g., a force transducer or high bandwidth pressure sensor), acurrent transducer, a voltage sensor, any other suitable sensed value,or any combination thereof.

In an illustrate example of step 1714, the control circuitry maydetermine a least norm solution of desired phase currents, in real time,based on force constants (e.g., which depend on position information), adesired force, and any constraints (e.g., currents must sum to zero, oreach current must be within a predetermined range). The control systemmay select an objective function (e.g., that the sequence of products ofeach phase current and corresponding force constant for a motor sum to adesired force, as shown by Eq. 5), and a constraint (e.g., the currentssum to zero). If all of the phase resistances ohmic R_(j) are the same,a set of current values may be determined using Eq. 6:

F _(DES)=Σ_(j=1) ^(N) k _(j)(x,Φ _(T))i _(j)  Equation 5:

i=k(k ^(T) k)⁻¹ F  Equation 6:

in which i is a column vector of the set of current values i_(j) of Nphases, k is column vector of the force constants k_(j)(x,Φ_(T)) of theN phases (e.g., based on position x and flux Φ_(T)), and F is a 1×1array (i.e., a scalar) having a value equal to the desired electromotiveforce F_(des) between the stator and the translator. This particularselection of objective function and constraint allows a least normsolution. If the phase resistances are not equal, for example, thecontrol system may determine a weighted least norm solution (e.g., byusing a weighted current variable, and then transforming to current).If, additionally, the sum of the currents is constrained to zero, forexample, Eq. 6 may still be used, although the arrays k and F aredefined differently. For example, k is a N×2 array with the first columnall ones, and the second column the set of force constants. Accordingly,F would be a 2×1 array, with the top row having a value of zero, and thebottom row having a value F_(des). A least norm solution, or weightedleast norm solution, may be achieved, for example, when a suitablequadratic objective function and affine equality constraint(s) are used.

In some embodiments, the control circuitry determines a desiredtrajectory of the translator (e.g., having apex positions to define astroke). The desired electromagnetic force, and phase currents derivedthereof, may be determined based on a desired position, a desiredvelocity, a desired acceleration, the desired trajectory, any othersuitable aspects of operation, or any combination thereof. Duringbraking (e.g., step 1708), the control circuitry may cause thetranslator to achieve one or more modified apex positions (e.g., closerto a mid-stroke position than a first apex position), to reduce thetrajectory (e.g., stroke length, peak velocity, or both).

Step 1716 includes the control circuitry causing the power electronicssystem to apply current for phase j based on the determined desiredcurrent of step 1714. In some embodiments, the control circuitrygenerates a control signal based on, and indicative of, the determineddesired current for phase j from step 1714. For example, the controlsignal may include a digital signal (e.g., a binary zero or one, a PWMsignal, a pulse signal), a message (e.g., a UDP or TCP messagetransmitted over ethernet), an analog signal (e.g., an analog voltage orcurrent signal), any other suitable signal, modulation thereof, or anycombination thereof. In some embodiments, the control signal istransmitted to the power electronics system, causing a current to beapplied to phase j. For example, the control circuitry may transmit aPWM signal to the power electronics system, which may in response applya current to phase j. The applied current may be close in value to thedesired current, or may differ from the desired current depending on,for example, how well the system is modeled, what perturbations arepresent, the accuracy of one or more sensors, or any other suitablefactors which may affect the application of current.

In some embodiments, after the control circuitry causes the current tobe applied to phase j, the control circuitry may repeat step 1702 asshown in FIG. 17. Accordingly, the control circuitry can periodicallycheck whether an event has occurred, while still performing process 1770repeatedly during, for example, normal operation. In some embodiments,the control circuitry proceeds to step 1710 after completing step 1716(e.g., to maintain normal operation), only returning to step 1702 at aless frequent periodicity (e.g., every N time steps where N is aninteger, once per stroke, or other suitable schedule).

It is contemplated that the steps or descriptions of FIG. 17 may be usedwith any other embodiments of this disclosure. In addition, the stepsand descriptions described in relation to FIG. 17 may be done inalternative orders or in parallel to further the purposes of thisdisclosure. For example, each of these steps may be performed in anyorder or in parallel or substantially simultaneously to reduce lag orincrease the speed of the system or method. Any of these steps may alsobe skipped or omitted from the process. Furthermore, it should be notedthat any of the systems and controllers discussed in relation to FIGS.12-14 could be used, alone or in concert, to perform one or more of thesteps in FIG. 17.

FIG. 18 shows a flowchart of illustrative process 1800 for managingshorting one or more phases of a multiphase electromagnetic machine, inaccordance with some embodiments of the present disclosure.

Step 1802 includes the control circuitry causing the power electronicssystem to short phase j. Step 1804 includes the control circuitrymeasuring one or more parameters for phase j, while shorted. Step 1806includes the control circuitry determining a suitable polarityindicative of a back emf in phase j. The performance of steps 1802,1804, and 1806 by the control circuitry allows the sign of current to beapplied to a phase J consistent with braking a translator. This isimportant for robust auto-braking, because current of the opposite sign(i.e., in which Vphase and the phase current have the same sign) resultsin a force in the direction of motion of the translator, thus addingenergy to the translator via work, and possibly creating a dangerous, ormore dangerous, situation.

In an illustrative example, referencing FIG. 12, step 1802 may includemotor controller 1260 causing power electronics system 1230 to shortphase lead 1242 and phase lead 1244 together. The short may beaccomplished by power electronics system 1230 actuating one or morecontactors that electrically short phase leads 1242 and 1244. In someembodiments, power electronics system 1230 includes a shorting circuit,which includes, for example, one or more sensors such as a voltagesensor, one or more passive circuit elements (e.g., a resistor, acapacitor, an inductor), one or more active circuit elements (e.g., avoltage source, a filter, a diode, a fuse), any other suitablecomponents, or any suitable combination thereof.

It is contemplated that the steps or descriptions of FIG. 18 may be usedwith any other embodiments of this disclosure. In addition, the stepsand descriptions described in relation to FIG. 18 may be done inalternative orders or in parallel to further the purposes of thisdisclosure. For example, each of these steps may be performed in anyorder or in parallel or substantially simultaneously to reduce lag orincrease the speed of the system or method. Any of these steps may alsobe skipped or omitted from the process. Furthermore, it should be notedthat any of the systems and controllers discussed in relation to FIGS.12-14 could be used, alone or in concert, to perform one or more of thesteps in FIG. 18.

FIG. 19 shows a flowchart of illustrative process 1900 for managingbraking a translator of a multiphase electromagnetic machine, inaccordance with some embodiments of the present disclosure.

Step 1902 includes control circuitry measuring a current in phase j. Insome embodiments, the control circuitry continuously receives a signalfrom a current sensor, and samples the signal at some suitable samplingrate to retrieve discretized values. Accordingly, in some embodiments,the control circuitry measures current in phase j at a fixed samplerate. The control circuitry may determine a current in phase j based ona calibration (e.g., relating a signal voltage to a current value), alook-up table, an algorithm, any other suitable technique, or anycombination thereof. In some embodiments, the control circuitry providespower to a current sensor, and samples a signal from the sensorindicative of current (e.g., a 4-20 mA loop current sensor outputpowered at a constant DC voltage). In some embodiments, at step 1902,the control circuitry need not measure current (i.e., in units of ampsor milliamps), and may measure a signal proportional to current (e.g.,voltage output of a current sensor not converted into units of current).

Step 1904 includes control circuitry retrieving a polarity indicative ofback emf in phase j. The polarity information may be provided by, forexample, stored information determined as a result of process 1800 ofFIG. 18. For example, the control circuitry may short phase j todetermine a polarity of back emf, store the polarity information, andthen retrieve the polarity information at step 1904 (e.g., at a latertime than the shorting).

Step 1906 includes control circuitry generating a control signal forphase j based on the measured current of step 1902 and the retrievedpolarity of step 1904. In some embodiments, the measured current of step1902 is used by the control circuitry as part of a feedback loop todetermine a current command, a control signal, or both. In someembodiments, the polarity of step 1904 is used by the control circuitryto determine the polarity of the desired current. In an illustrativeexample, controller 2200 is configured to generate a control signalbased on a measured current and a determined polarity indicative of backemf.

Step 1908 includes control circuitry causing a current to be applied tophase j based on the control signal. In some embodiments, the controlcircuitry transmits the generated control signal of step 1906 to a powerelectronics system, which applies current to phase j based on thecontrol signal. In an illustrative example, the control circuitry maygenerate a PWM signal, and transmit the PWM signal to the powerelectronics system. The power electronics system may process the PWMsignal (e.g., level-shift, amplify, isolate, filter, or otherwisemodify), and apply a corresponding current to phase j. To furtherillustrate, a PWM signal or processed signal derived thereof, may beused to directly activate a switch, and may be coupled to a gate orother control terminal of the switch) which couples a bus to a phaselead.

It is contemplated that the steps or descriptions of FIG. 19 may be usedwith any other embodiments of this disclosure. In addition, the stepsand descriptions described in relation to FIG. 19 may be done inalternative orders or in parallel to further the purposes of thisdisclosure. For example, each of these steps may be performed in anyorder or in parallel or substantially simultaneously to reduce lag orincrease the speed of the system or method. Any of these steps may alsobe skipped or omitted from the process. Furthermore, it should be notedthat any of the systems and controllers discussed herein may be used,alone or in concert, to perform one or more of the steps in FIG. 19.

In some embodiments, the control circuitry performs a braking processwhich includes synchronizing two opposing translators. For example,considering an opposed free-piston linear generator having twotranslators, it may be desired to synchronize the two translators duringbraking to maintain a predictable and safe shutdown (e.g., avoidingdamage of components, or unstable operation). Accordingly, the controlcircuitry may use position information of the translators to provide atleast some synchronization of translators. The following discussion, inthe context of FIGS. 20-23, describes the braking process taking intoaccount position information, in accordance with some embodiments. Thetechniques of processes 1700, 1800, and 1900 may be used in accordancewith auto-braking with synchronization. In some embodiments, thetechniques may be applied to a high-phase count configuration, whereeach individual phase (i.e., iron core and corresponding winding) iscontrolled independently.

FIG. 20 shows illustrative system 2000, including a multiphaseelectromagnetic machine 2040 having two translators 2015 and 2005, inaccordance with some embodiments of the present disclosure. System 2000includes control system 2050, motor controllers 2023 and 2033, powerelectronics systems 2022 and 2032, optional sensors 2031 and 2021, andmultiphase machines 2006 and 2016. Multiphase machine 2006 includes, forexample, translator 2005, and phases 2001, 2002, 2003, and 2004.Multiphase machine 2016 includes, for example, translator 2015, andphases 2011, 2012, 2013, and 2014.

Translator 2005 is configured to translate along axis 2007, andtranslator 115 is configured to translate along axis 2017. Under normaloperating circumstances, translators 2005 and 2015 move nominally inopposed fashion. Although there may be some perturbation, thetrajectories of translators 2005 and 2015 are substantially similar.During a stroke (i.e., motion of a translator from one apex to anotherapex), magnets of a translator (not shown in FIG. 20) pass phases of thecorresponding stator. While the magnets are aligned at least partiallywith a phase, an electromagnetic interaction may occur between thetranslator and the phase. For example, referencing FIG. 20, translator2015 may electromagnetically interact with phases 2012-2014, but notinteract significantly with phase 2011. As translator 2015 movesin-board (i.e., opposite the illustrated direction of axis 2017) fromits illustrated position in FIG. 20, the magnets will eventually be nearphase 2011, and an electromagnetic interaction may occur. Accordingly,the interaction between a phase and a translator depends on the positionof the translator relative to the phase.

System 2000 optionally includes sensors 2021 and 2031, which may beconfigured to sense position information of respective translators 2005and 2015 relative to respective phases 2001-2004 and 2011-2014. In someembodiments, sensors 2021 and 2031 are not included, not used forbraking, or may otherwise be omitted from system 2000. For example,sensors 2021 and 2031 may include an encoder, a search coil, a proximitysensor, any other suitable sensor for sensing position information, orany combination thereof. Position information includes, for example, aposition (e.g., a relative or absolute position), a velocity, anacceleration, a binary value indicative of a relative position (e.g.,past a reference location), an index (e.g., which phase a terminal endof the translator is aligned with), information which may be used todetermine position (e.g., sinusoidal encoder signals), any othersuitable information indicative of position, or any combination thereof.Sensors 2021 and 2031 may be coupled to respective motor controllers2023 and 2033, control system 2050, or a combination thereof.

Power electronics systems 2022 and 2032 are configured to apply currentto phases 2001-2004 and 2011-2014, respectively (e.g., by performingprocess 1770 of FIG. 17). In some embodiments, power electronics systems2022 and 2032 each include switches (e.g., IGBTs, MOSFETS or any othersuitable switches), diodes, brake resistors, control signal interfaceboards (e.g., for managing PWM signals), current sensors, any othersuitable components, or any combination thereof. In some embodiments,power electronics systems 2022 and 2032 are configured to short phasesof respective multiphase machines 2006 and 2016 (e.g., perform shortingprocess 1800 of FIG. 18). In some embodiments, power electronics systems2022 and 2032 are configured to measure phase voltages in respectivephases 2001-2004 and 2011-2014. For example, in some embodiments, powerelectronics systems 2022 and 2032 are configured to measure phasevoltages in respective phases when no current is applied (e.g., thephases are not coupled to a DC bus or a neutral).

In some embodiments, control system 2050 is configured to, for example,process signals (e.g., from sensors or subsystems), generate controlsignals (e.g., to transmit to subsystems), execute computer readableinstructions for controlling multiphase machines 2006 and 2016. In someembodiments, control system 2050 may be distributed, partitioned,combined with other systems, or otherwise modified from system 2000shown in FIG. 20. In some embodiments, control system 2050 provides adesired current, a desired force, an operating state, a command, orother suitable information to motor controllers 2023 and 2033, whichgenerate respective control signals that are transmitted to respectivepower electronics systems 2022 an 2032. In some embodiments, forexample, control system 2050 provides desired current values for eachphase to the corresponding power electronics system.

In some embodiments, motor controllers 2023 and 2033 are configured toprovide control signals to respective power electronics systems 2022 and2032. In some embodiments, motor controllers 2023 and 2033 areconfigured to receive signals from respective sensors 2021 and 2031. Insome embodiments, each of motor controllers 2023 and 2033 is configuredto receive signals from both sensors 2021 and 2031.

In some embodiments, communication link 2042 (“comm link 2042”) includesa path for communication between motor controllers 2023 and 2033. Commlink 2042 may be used to allow communication among more than onetranslator-stator machine (e.g., a multiphase machine having twotranslators). Further, in some embodiments, motor controllers 2023 and2033 include a common communication bus internally, in which informationfor each phase of the respective motor is transmitted. Comm link 2042may include, for example, a common bus, to which all phase controllersare coupled and are configured to pull up, pull down, or otherwiseaffect the common bus to transmit information to each other.Accordingly, in some embodiments, comm link 2042 allows for simple(e.g., 1 or 2 wires, with information in the form of pulses, edges orlevels) yet fast and reliable communication among motor controllers,phase controllers thereof, or both. In some embodiments, comm link 2042is capable of transmitting signals having more information, andrelatively more complex features (e.g., modulated signals, digitalcommunication, network communication).

In some embodiments, a position estimator is distributed across phases,and communication is established among control circuitry coupled to eachcorresponding phase of each opposed LEMs. Accordingly, any suitabletechnique disclosed herein can be used to maintain synchronization ofthe opposed multiphase machines while braking. A dedicated communicationlink (e.g., comm link 2042 of FIG. 20) may be included for thisfunction, among the phase controllers. The communications link need notbe capable of transmitting complex signals. For example, the signal mayinclude a simple edge signal (a “tick”) corresponding to the detectionof the first magnet of the translator reaching the corresponding toothof each phase. A simple trigger signal, from each phase controller, maybe sent to the corresponding phase controller of the opposed motor,using any available electrical or optical technique. The signals ofopposed phases can eventually be compared (e.g., using OR logic), forexample, to limit the number of conductors. In some such embodiments,while auto-braking, the translator that appears to be faster, or leading(i.e. the one that senses a magnet first on the phase of interest),immediately starts braking, while the opposed phase controller waits fora predetermined time before engaging the auto-brake mechanism (e.g.,process 1900 of FIG. 19). Accordingly, the opposed phase controllercauses a corresponding power electronics system to extract relativelyless energy from the “late” or “slow” translator (e.g., until bothtranslators are synchronized again). Accordingly, control circuitry(e.g., phase controllers or motor controllers) may maintainsynchronization during “auto-brake,” even if a central controller (e.g.,control system 350 of FIG. 3 or control system 2050 of FIG. 20) stopsoperating or is otherwise unavailable or unreliable. In someembodiments, an idle time is determined (e.g., from computation) as afunction of the measured time between the two ticks, to ensureconvergence. In some embodiments, a simple gain is used, although anysuitable processing may be used, having any suitable complexity, inaccordance with the present disclosure. In some embodiments, translatorposition, velocity, or other position information is used to optimizethe synchronization performance of the control circuitry.

FIG. 21 shows a flowchart of illustrative process 2100 for managingbraking a translator of a multiphase electromagnetic machine based onposition information of the translator, in accordance with someembodiments of the present disclosure. Control circuitry may performprocess 2100, or any step thereof, to slow or stop a translator.

Step 2102 includes the control circuitry detecting an event, orotherwise determining an event has occurred. In some embodiments, theevent may include a fault event or a failure event. For example, anevent may include a loss of communication between subsystems of acontrol system (e.g., control system 350 of FIG. 3). In a furtherexample, an event may include an unintended short of a phase in amultiphase electromagnetic machine (e.g., multiphase electromagneticmachine 340 of FIG. 3). In a further example, an event may include aloss in signal from a sensor as received by a control system (e.g., anencoder, a phase current sensor, or a DC bus voltage sensor). In afurther example, an event may include a mode change to “stop” from acontrol system, during which braking is desired. In some embodiments,control circuitry may determine an event has occurred by performing aset of diagnostics (e.g., checking that signals are refreshing, checkingthat sensors are providing signals, checking that all communicationsbetween systems and subsystems are occurring).

Depending upon whether the control circuitry has detected an event atstep 2102, the control circuitry may proceed to either step 2104, orprocess 2112. Process 2112 is an illustrative process performed when noevent has been detected (e.g., normal operation).

Step 2104 includes the control circuitry determining how to manage phasej to achieve braking in response to a detected event. In someembodiments, managing phase j includes determining whether to performshorting process 2106, perform position estimation process 2108, performbraking process 2110, or stop auto-braking 2150. In some embodiments,step 2104 is repeated for all phases of a multiphase electromagneticmachine. In some embodiments, the control circuitry may execute apredetermined schedule of performing shorting process 2106, positionestimation process 2108, braking process 2110, and performing stoppingauto-brake 2150. The predetermined schedule may include time durationsand intervals for performing the processes.

For example, at step 2104, the control circuitry may perform positionestimation process 2108 to estimate position, followed by shortingprocess 2106 to determine a polarity indicative of back emf in phase j,and then perform braking process 2110 to extract energy from thecorresponding translator. In a further example, at step 2104, thecontrol circuitry may repeat process 2108 until the position has beenestimated, which may include determining phase voltage at no currentflow for each phase to estimate position. When the position isestimated, the control circuitry may then perform shorting process 2106repeatedly to determine the polarity of each phase that may interactelectromagnetically with the translator (e.g., the set of phases that jincludes). Finally, the control circuitry may perform braking process2110 based on the polarity, or polarities, determined at step 2106. Thecontrol circuitry may then repeat step 2108, step 2106, or both, at someinterval to track the translator(s) position and back emf while braking.Because phase j cannot simultaneously 1) be shorted (e.g., phase leadscoupled together), 2) have no current flow (e.g., phase leads isolatedfrom one another), and 3) have current applied (e.g., an applied Vphasefrom a DC bus which causes current flow), processes 2106, 2108, and 2110are not performed by the control circuitry at the same instant.

In some embodiments, shorting process 2106 includes any or all suitablesteps of process 1706 of FIG. 17, or process 1800 of FIG. 18.

In some embodiments, braking process 2106 includes any or all suitablesteps of process 1708 of FIG. 17, or process 1900 of FIG. 19.

Position estimation process 2108 is further described in the context ofprocess 2200 of FIG. 22. FIG. 22 shows a flowchart of illustrativeprocess 2200 for position estimation, in accordance with someembodiments of the present disclosure.

To accomplish synchronization between two translators, positioninformation is needed for each translator to determine the relativelead/lag, and which requires more or less braking. Accordingly, process2250 includes position estimation for one translator, and process 2260includes position estimation for the other translator. Also, processes2250 and 2260 may be, but need not be, similar or identical. Thefollowing description will be framed in terms of process 2250 (i.e., forphase j of one translator), and it will be understood that thediscussion applies to process 2260 (i.e., for phase k of the othertranslator).

Step 2202 includes the control circuitry causing no current to flow inphase j. In some embodiments, step 2202 includes the control circuitrynot generating a control signal. In some embodiments, step 2202 includesthe control circuitry generating a null control signal (e.g., desiredcurrent of zero amps, or a PWM with zero duty cycle, other suitablesignal). The control circuitry may optionally proceed to step 2204,2206, 2208, or a combination thereof depending on the techniqueemployed. For example, in some embodiments, the control circuitrymeasures Vphase at step 2204, and then proceeds to step 2210. In afurther example, in some embodiments, the control circuitry comparesVphase to a reference at step 2206, and then proceeds to step 2210. In afurther example, in some embodiments, the control circuitry identifies atick at step 2208, and then proceeds to step 2210. In a further example,the control circuitry measures Vphase at step 2204, compares it to areference at step 2206, and then identifies a tick in the comparison atstep 2208 to determine a position metric.

In some embodiments, the control circuitry need not include an absoluteposition estimator for each phase. In some embodiments, the controlcircuitry need not include a sensor for each phase controller, of eachrespective motor. Accordingly, in some embodiments, a “tick” signalprovides sufficient information to auto-brake with synchronization.

Step 2204 includes the control circuitry measuring, or otherwisedetermining an indication of, Vphase in phase j. In some embodiments, avoltage transducer is coupled across phase leads of phase j and providesa signal indicative of Vphase to the control circuitry, which isconfigured to receive the signal. In some embodiments, the controlcircuitry uses a sampled voltage value from the sensor to determine avalue indicative of Vphase. In some embodiments, the control circuitryuses a sampled voltage value from the sensor, modified by a calibration,to determine a value of Vphase (i.e., in relevant units, sign, andmagnitude). In some embodiments, the control circuitry performs signalprocessing on the signal received from the sensor, to generate aprocessed signal for determining Vphase, or an indication thereof.

Step 2206 includes the control circuitry comparing Vphase in phase j, oran indication thereof, to a reference signal. In some embodiments, aphase controller includes a comparator circuit configured to compareVphase of phase j to a reference voltage. For example, the comparatorcircuit may output one of two binary values indicating if Vphase isgreater than, or less than, the reference voltage. In some embodiments,a phase controller may compare a signal indicative to Vphase to areference in software as a mathematical operation, outputting adifference, a binary value, or other suitable output. In someembodiments, the control circuitry first performs step 2204 to determineVphase, and then compares the Vphase value to a reference value (e.g., athreshold).

Step 2208 includes the control circuitry identifying a tick in a Vphasesignal, or signal derived thereof. In some embodiments, the “tick” isgenerated by a voltage comparator, configured to compare the phasevoltage to a reference value when no current is flowing in phase j.Under the no current condition, the phase voltage equals, or mayotherwise be approximated by, the back emf (e.g., as shown by Equation4). As a first magnet of the translator (e.g., a magnet at either end ofa magnet array) axially passes a tooth of phase j, it may be detectedwhen the phase voltage reaches a given threshold. The control circuitrymay identify the threshold crossing and accordingly may estimate atranslator position. In some embodiments, the voltage threshold levelmay be adjustable, for example, to achieve improved position precision.For example, a region or point of high dV_(phase)/dx (i.e., phasevoltage gradient in terms of translator position) may indicate that atooth of a phase and a magnet are transitioning between overlapping andnon-overlapping, or vice versa. In some embodiments, a voltagecomparator may be implemented using a transistor, an operationalamplifier, an integrated circuit, or any other suitable comparator.

Step 2210 includes the control circuitry determining a position metricof the translator. In some embodiments, the control circuitry repeatsstep 1302 and any suitable combination of steps 2204-2208 to determinethe position metric. The position metric may include a phase index(e.g., which phase j exhibits a tick), a spatial position estimate(e.g., an axial position or position range), a timestamp of when amagnet overlapped a phase j, any other suitable position information, orany combination thereof.

Step 2220 includes the control circuitry determining a position metricof the other translator. In some embodiments, the control circuitryrepeats step 2212 and any suitable combination of steps 2214-2218 todetermine the position metric. The position metric may include a phaseindex (e.g., which phase k exhibits a tick), a spatial position estimate(e.g., an axial position or position range), a timestamp of when amagnet overlapped a phase j, any other suitable position information, orany combination thereof. In some embodiments, the control circuitry maydetermine a position of a translator, or portion thereof (e.g., aleading edge of a magnet), at step 2220.

Step 2222 may include the control circuitry determining asynchronization metric based on the position metrics determined at steps2210 and 2220 for the two respective translators. In some embodiments,the control circuitry may compare the position metrics for the twotranslators to determine which translator is moving more quickly, movingmore slowly, leading in position, lagging in position, or a combinationthereof. In some embodiments, the control circuitry may comparetimestamps for when respective first magnets of the two translatorsoverlapped opposite phases to determine which translator is leading orlagging. A synchronization metric may include, for example, a time(e.g., time at which a tick for a phase occurs), an indexed time (e.g.,“first” or “last”), a spatial position (e.g., 0.02 meters), an indexedposition (e.g., “at or near phase j”), any other suitable metric, or anycombination thereof.

In some embodiments, a communication protocol is used to communicateticks among phase controllers. For example, in some embodiments, asingle, multiplexed bus is used for all the “tick” signals from thephases. In a further example, a relatively simple and low-cost “bus”(e.g., which could just be a single wire) may be implemented on whichevery phase controller sends its tick by pulling the bus line up ordown. Accordingly, this may help in limiting the number of conductorsrequired between the two motor controllers corresponding to the tworespective translators. For example, a “tick” signal may be sent only asan end magnet appears near, or begins to overlap with, a phase winding.Accordingly, at that time that phase should be the only phase exhibitinga tick, and the likelihood of any conflict on the single bus is reduced(e.g., also reducing signal delays on the bus).

Any suitable combination of auto-brake, and auto-brake withsynchronization may be used, in accordance with the present disclosure.For example, when the first or last magnet on the magnet carrier (e.g.,magnets on the ends axially of the magnet array) axially passing a phaseis the detected event, it may be challenging, or impossible, to get a“tick” feature from the central phases (e.g., because they will likelynot see a magnet/no-magnet transition). In some such circumstances, thecentral or middle phases may be used for “auto-brake” only (e.g., asdescribed in the context of step 1708 of FIG. 17), without taking intoaccount the position information.

In some embodiments, a “halt” signal is sent from one phase to itscounterpart on the other multiphase electromagnetic machine, when itsauto-brake is deactivated for reasons other than synchronization (e.g.,a DC bus overvoltage, a dead MOSFET or IGBT, etc.). The phase would thusprevent its counterpart from braking whether or not the magnet carrieris present over the phase, thus actively helping preventdesynchronization.

In some embodiments, the detection of the magnet carrier is achieved byimplementing a comparator circuit on the phase voltage. In someembodiments, the comparator is realized with a single transistor. Forexample, a star configuration may be used (e.g., comparators spanning aphase winding from the power electronics system to a neutral wye),provided the neutral is accessible on the motor (e.g., for a wyeconnected motor). In circumstances in which the motor neutral is notaccessible, the neutral may be reconstructed as the average of all phasevoltages.

Polarity Determination Based on PWM

FIG. 23 shows a flowchart of illustrative process 2300 for determining apolarity associated with a phase, in accordance with some embodiments ofthe present disclosure. In some embodiments, a control system performsprocess 2300 in response to an event being detected. In someembodiments, the control system may perform process 2300 prior to anevent being detected. While the description of process 2300 is providedin the context of a PWM duty cycle (e.g., a control signal for phasecurrent), any suitable parameter (e.g., current, current derivative,magnetic flux, emf, phase voltage, or other parameter) or metric derivedthereof, or combination thereof, may be used in accordance with thepresent disclosure.

Step 2302 includes initializing a polarity value. In some embodiments,the control system initializes the polarity based on a polarity duringnormal operation. For example, when an event is detected, the controlsystem may use the last determined polarity, or determine the lastpolarity based on available information, to initialize the polarityduring braking. In an illustrative example, a polarity may be one of twovalues (e.g., a binary state such as positive or negative).

Step 2304 includes defining one or more duty cycle thresholds. In someembodiments, a duty cycle threshold includes a predetermined value(e.g., a predetermined duty cycle value). In some embodiments, the dutycycle threshold may depend on an operating parameter. For example, thethreshold may be based on peak current, peak translator velocity, poweroutput, peak duty cycle, motor electrical frequency (e.g., a frequencyof polarity changes), a time period between threshold crossings, anyother suitable parameter, or any combination thereof. A duty cyclethreshold may include any suitable numerical value, including zero.

Step 2306 includes determining a duty cycle state. In some embodiments,the control system may use the last duty cycle value as the duty cyclestate. In some embodiments, the control system may use a filtered value(e.g., using an FIR or IIR filter) based on historical duty cyclevalues. The duty cycle state may include a desired duty cycle, anachieved duty cycle, an average duty cycle, a representative duty cycle(e.g., determined based on a model, algorithm or other suitablecalculation), a duty cycle determined based on other availableparameters, any other suitable duty cycle value, or any combinationthereof.

Step 2308 includes comparing the duty cycle state to a duty cyclethreshold of step 2304. In some embodiments, the threshold used dependson a property of the duty cycle state. For example, in some embodiments,the polarity of the threshold is matched to the polarity of the dutycycle state. In some embodiments, an absolute value of the duty cycle iscompared to a threshold value having a positive sign.

Step 2310 includes again comparing the duty cycle state to a duty cyclethreshold. In some embodiments, a second crossing of the duty cyclestate and the threshold is used to estimate when polarity has switched,is about to switch, is likely to switch, or otherwise has a highprobability of switching. In some embodiments, upon the secondcomparison, the control system may proceed to step 2312.

Step 2312 includes switching the initialized polarity. In someembodiments, the control system may update a flag, update a storedvalue, update a parameter value, or otherwise provide an instruction toindicate the switch.

Step 2314 includes outputting the switched polarity. In someembodiments, step 2314 includes a central controller outputting thepolarity to a phase controller or motor controller. In some embodiments,the control system may output the polarity for storage in memory to beused to determine a phase current. In some embodiments, the controlsystem may output the polarity to another algorithm or portion ofalgorithm to estimate a translator position, a translator velocity,estimate a phase current (e.g., a desired current or an appliedcurrent).

In an illustrative example, process 2300 may be applied during braking,while maintaining a braking current for each phase at a fixed relativemagnitude, although the polarity switches, depending on translatorposition (e.g., magnetic pole positions relative to the phase). In thisillustrative example, phase current information is available. At step2302, the control system may initialize a polarity value to “positive.”At step 2304, the control system may define a near-zero, but nonzero,threshold value. At step 2306, the control system may determine a recentPWM value (e.g., the last PWM value), indicative of the control signalduty cycle required for the power electronics system to maintain thecurrent. At step 2308, the control system may determine whether theproduct of the determined duty cycle and the initialized polarity isgreater than the threshold (e.g., positive value here). If the productof the determined duty cycle and the initialized polarity is greaterthan the threshold, then the control system returns to step 2306 andrepeats. If the product of the determined duty cycle and the initializedpolarity is not greater than the threshold, then the control systemproceeds to step 2310. In some embodiments, at step 2310, the controlsystem determines whether the threshold crossing is the second crossingsince the last polarity switch. In some embodiments, at step 2310, thecontrol system determines when the next threshold crossing after step2308 occurs. When the polarity of the determined duty cycle switches,the threshold value may switch as well. At step 2310, the control systemmay determine that the product of the determined duty cycle and theinitialized polarity (i.e., now negative) is not greater than thethreshold (i.e., also negative), and proceed to step 2312. At step 2312,the control system switches the polarity to “negative,” and at step2314, the control system outputs the negative polarity. Process 2300continues until braking is completed. Illustrative panel 2350 shows theaforementioned example. In some embodiments, the absolute value of thedetermined duty cycle is compared to a positive threshold value. In someembodiments, not using absolute value, where the product of thedetermined duty cycle and the present polarity compared with thethreshold value, the threshold value changes sign only when polarity ischanged. Table 1 shows an illustrative state diagram corresponding toillustrative panel 2350.

In some circumstances, an event may include a fault event associatedwith a DC bus, a component coupled to the DC bus, a grid tie inverter,an AC grid, or a combination thereof. In some such circumstances, the DCbus may be compromised, unregulated, or otherwise unreliable to transferenergy from a translator to an AC grid. A brake resistor allows forenergy dissipation, which may

TABLE 1 Illustrative state diagram of panel 2350 of FIG. 23. IndexComparison Polarity Dthreshold A D × Polarity > Dthreshold, True 1 +0.05B D × Polarity > Dthreshold, True 1 +0.05 C D × Polarity > Dthreshold,False  1 → −1 +0.05 D D × Polarity > Dthreshold, False −1  −0.05 E D ×Polarity > Dthreshold, True −1  −0.05 F D × Polarity > Dthreshold, False−1 → 1 −0.05 G D × Polarity > Dthreshold, False 1 −0.05help to brake a translator. In some embodiments, a brake resistor may becoupled to phase leads to remove energy, in addition to the controlsystem performing one or more of the disclosed braking techniques. Forexample, in order to controllably slow a translator to a stop (e.g.,stop reciprocating), the use of a brake resistor may accompany theapplication of phase currents to generate a force that opposestranslator motion. In some embodiments, the use of a brake resistorstill requires a functioning motor controller (e.g., one or more phasecontrollers having position information, current information, or both)and a functioning power electronics system. FIG. 24 shows a blockdiagram of illustrative power electronics system 2400 having brakeresistor 2440 and switch 2450, and one phase of a multiphase machine, inaccordance with some embodiments of the present disclosure. FIG. 25shows a flowchart of illustrative process 2500 for engaging a brakeresistor, in accordance with some embodiments of the present disclosure.Step 2502 of FIG. 25 includes detecting an event (e.g., a fault event ora failure event), and step 2504 includes closing a switch to engage abrake resistor in response to the detection.

System 2400 includes an H-bridge configuration including switches2414-2417 and fly-back diodes 2434-2437 coupled to phase 2460 of anelectromagnetic machine by phase leads 2461 and 2462. The H-bridge iscoupled to DC bus 2402, which may be regulated or otherwise maintainedby a grid tie inverter or other suitable equipment, for example. Currentsensor 2408 is configured to sense current in phase 2460 and output asensor signal to a control system, for example. The electromagneticmachine may include multiple phases, each coupled by a respectiveH-bridge. Although shown as coupled to an H-bridge, in some embodiments,phase 2460 may be coupled to a wye-neutral connection (e.g., included ina star configuration). Accordingly, in some such embodiments, only twoswitches, rather than four, are used, with the other side of theH-bridge replaced by a neutral connection (e.g., resulting in a halfH-bridge). Any suitable switch topology may be used in the context ofprocess 2500.

Switches 2414-2417 may include transistors or any other suitablecontrollable solid-state switches. For example, switches 2414-2417 mayinclude IGBTs, MOSFETs, or other suitable switches for which the controlsystem is coupled to the respective gate terminals 2424-2427 configuredto open or close the corresponding switches (e.g., gate terminals mayeach include two terminals to produce a voltage difference in someembodiments). Switches 2414-2417 are configured in parallel withrespective fly-back diodes 2434-2437 to prevent large voltage spikeswhen switched (e.g., due to the inductance of phase 2460). Switches 2414and 2416 may be referred to as high-voltage switches (e.g., coupled to ahigh-voltage bus line of DC bus 2402). Switches 2415 and 2417 may bereferred to as low-voltage switches (e.g., coupled to a low-voltage busline of DC bus 2402). Further, switches 2414 and 2415 may be associatedwith a first side of the H-bridge, and switches 2416 and 2417 may beassociated with a second side of the H-bridge.

Switch 2450 may include any suitable switch such as, for example, atransistor, a contactor, a relay, any other suitable controllable switchor any combination thereof. Switch 2450 is open (i.e., not forming anelectrically conductive path) during normal operation, such that it doesnot short DC bus 2402 through brake resistor 2440 (e.g., thus wastingenergy). When an event is detected, the control system may close switch2450 (e.g., forming an electrically conductive path), thus couplingbrake resistor 2440 to both bus lines of DC bus 2402. Accordingly, whenbraking, brake resistor will experience a voltage drop equal to, ornearly equal to, the voltage across DC bus 2402. The voltage across DCbus 2402 may be hundreds of volts, or more, for example. During braking,brake resistor 2440 dissipates energy according to its ohmic loss. Forexample, the dissipated power is determined from Power=I²R, whiledissipated energy is equal to integral of Power over time. In anillustrative example, because switch 2450 undergoes a one-or-two throwcadence during a normal operation-to-braking-to-stopped cadence (e.g.,off-on, or off-on-off), switch 2450 may include a contactor or othernon-solid-state switch (e.g., because it is not typically cycled at highfrequency).

Passive Brake with Half-Wave Rectifier (2 Diodes)

In some embodiments, a half-wave rectifier may be used in conjunctionwith a brake resistor to cause a translator to brake. The half-waverectifier may include two diodes coupling a phase to a brake resistor.FIG. 26 shows a block diagram of illustrative power electronics system2600 having brake resistor 2640, switch 2650 and diodes 2671-2672, andone phase of a multiphase machine, in accordance with some embodimentsof the present disclosure. Illustrative process 2500 of FIG. 25 forengaging a brake resistor may be applied to system 2600, with theadditional consideration that step 2502 includes maintaining switches2614-2617 open, in accordance with some embodiments of the presentdisclosure.

System 2600 includes an H-bridge configuration including switches2614-2617 and fly-back diodes 2634-2637 coupled to phase 2660 of anelectromagnetic machine by phase leads 2661 and 2662. The H-bridge iscoupled to DC bus 2602, which may be regulated or otherwise maintainedby a grid tie inverter, for example. Current sensor 2608 is configuredto sense current in phase 2660 and output a sensor signal to a controlsystem, for example. The electromagnetic machine may include multiplephases, each coupled by a respective H-bridge. Although shown as coupledto an H-bridge, in some embodiments, phase 2660 may be coupled to aneutral connection (e.g., included in a star configuration).Accordingly, in some such embodiments, only two switches, rather thanfour, are used, with the other side of the H-bridge replaced by aneutral connection (e.g., resulting in a half H-bridge). Any suitableswitch topology may be used in the context of process 2500.

Switches 2614-2617 may include transistors or any other suitablecontrollable solid-state switches. For example, switches 2614-2617 mayinclude IGBTs, MOSFETs, or other suitable switches for which the controlsystem is coupled to the respective gate terminals 2624-2627 configuredto open or close the corresponding switches (e.g., gate terminals mayeach include two terminals to produce a voltage difference in someembodiments). Switches 2614-2617 are configured in parallel withrespective fly-back diodes 2634-2637 to prevent large voltage spikeswhen switched (e.g., due to the inductance of phase 2660). Switches 2614and 2616 may be referred to as high-voltage switches (e.g., coupled to ahigh-voltage bus line of DC bus 2602). Switches 2615 and 2617 may bereferred to as low-voltage switches (e.g., coupled to a low-voltage busline of DC bus 2602). Further, switches 2614 and 2615 may be associatedwith a first side of the H-bridge, and switches 2616 and 2617 may beassociated with a second side of the H-bridge.

Diode 2671 is coupled to phase lead 2661 and brake resistor 2640,allowing current flow only from phase lead 2661 to brake resistor 2640.Diode 2672 is coupled to phase lead 2662 and brake resistor 2640,allowing current flow only from phase lead 2662 to brake resistor 2640.Diodes 2671 and 2672 have similar polarity relative to brake resistor2640, creating a half-wave rectifier. The relative positions of brakeresistor 2640 and switch 2650 may be swapped (e.g., as long as they arein series, the order need not be as illustrated).

Switch 2650 may include any suitable switch such as, for example, atransistor, a contactor, a relay, any other suitable controllable switchor any combination thereof. Switch 2650 is open (i.e., not forming anelectrically conductive path) during normal operation, such that it doesnot interfere with operation of switches 2614-2617. When an event isdetected, the control system may close switch 2650 (e.g., forming anelectrically conductive path), and hold or otherwise maintain switches2614-2617 open. When switches 2614-2617 are all open, any emf generatedby a translator interacting with phase 2660 will cause a current to flowthrough either diode 2671 and 2672 to brake resistor 2640 (e.g., andsubsequently to the low-voltage bus line of DC bus 2602). In someembodiments, the control system need not apply a signal to gateterminals 2624-2627 to maintain respective switches 2614-2617 open(e.g., the gate terminals may be pulled down). During braking, brakeresistor 2440 dissipates energy from the induced current according toits ohmic loss. For example, the dissipated power is determined fromPower=I²R, while dissipated energy is equal to an integral of Power overtime. In an illustrative example, because switch 2450 undergoes aone-or-two throw cadence during a normal operation-to-braking-to-stoppedcadence (e.g., off-on, or off-on-off), switch 2450 may include acontactor or other non-solid-state switch (e.g., because it is nottypically cycled at high frequency).

In some embodiments, the control system may generate braking signals,and a power electronics system applies the braking signals to controlone or more switches coupled to a phase. For example, in the context ofan H-bridge configuration, the power electronics system may applysuitable braking signals to suitable switches to cause a translator tobrake. FIG. 27 shows illustrative braking signals for applying to apower electronics system, in accordance with some embodiments of thepresent disclosure. FIG. 28 shows a block diagram of illustrative powerelectronics system 2800 configured to receive braking signals, inaccordance with some embodiments of the present disclosure. FIG. 29shows a flowchart of illustrative process 2900 for applying brakingsignals, in accordance with some embodiments of the present disclosure.

Brake signals 2700 include signals applied to switches of a powerelectronics system, which may be configured to apply correspondingcurrents to phases of a multiphase electromagnetic machine. Brakingsignal 2701 includes a zero, or null signal, which is configured tomaintain a switch open. In some embodiments, the lack of an appliedsignal may constitute signal 2701. For example, the gate of a switch maybe pulled down to ground and in the absence of an applied signal, may bemaintained at zero volts. Braking signal 2702 includes both on and offintervals. For example, as illustrated in FIG. 27, braking signal 2702includes a PWM signal with roughly a 30% duty cycle. Brake signal 2702may include any suitable signal shape in time that includes on and offperiods. For example, brake signal 2702 may include a sinusoidal signal,a square wave, a triangular wave, a sawtooth wave, a chirp signal, awavelet, any other suitable shape or waveform, or modulation thereof,having a regular or irregular period, or any combination thereof.

System 2800 includes an H-bridge configuration including switches2814-2817 and fly-back diodes 2834-2837 coupled to phase 2860 of anelectromagnetic machine by phase leads 2861 and 2862. The H-bridge iscoupled to DC bus 2802, which may be regulated or otherwise maintainedby a grid tie inverter, for example. Current sensor 2808 is configuredto sense current in phase 2860 and output a sensor signal to a controlsystem, for example. The electromagnetic machine may include multiplephases, each coupled by a respective H-bridge. Although shown as coupledto an H-bridge, in some embodiments, phase 2860 may be coupled to aneutral connection (e.g., included in a star configuration).Accordingly, in some such embodiments, only two switches, rather thanfour, are used, with the other side of the H-bridge replaced by aneutral connection (e.g., resulting in a half H-bridge). Any suitableswitch topology may be used in the context of process 2900.

Switches 2814-2817 may include transistors or any other suitablecontrollable solid-state switches. For example, switches 2814-2817 mayinclude IGBTs, MOSFETs, or any other suitable switch for which thecontrol system is coupled to the respective gate terminals 2824-2827configured to open or close the corresponding switches (e.g., gateterminals may each include two terminals to produce a voltage differencein some embodiments). Switches 2814-2817 are configured in parallel withrespective fly-back diodes 2834-2837 to prevent large voltages whenswitched (e.g., due to the inductance of phase 2860). Switches 2814 and2816 may be referred to as high-voltage switches (e.g., coupled to ahigh-voltage bus line of DC bus 2802). Switches 2815 and 2817 may bereferred to as low-voltage switches (e.g., coupled to a low-voltage busline of DC bus 2802). Further, switches 2814 and 2815 may be associatedwith a first side of the H-bridge, and switches 2816 and 2817 may beassociated with a second side of the H-bridge.

Referencing FIG. 28, the control system may operate the H-bridge tobrake translator by activating either both the high-voltage switches orboth the low voltage switches, with the remaining switches maintainedopen (e.g., not activated). Table 2 shows illustrative control signals.Step 2902 of FIG. 29 includes detecting an event (e.g., a fault event),and step 2904 includes applying braking signals in response to thedetection (e.g., implementing modes Braking A or Braking B of Table 2).

TABLE 2 Illustrative control signals to H-bridge switches, for normaloperation and braking Switch 2814 Switch 2815 Switch 2816 Switch 2817Normal PWM based on PWM based on PWM based on PWM based on operationposition position position position Braking A Signal 2701 Signal 2702Signal 2701 Signal 2702 Braking B Signal 2702 Signal 2701 Signal 2702Signal 2701

As shown in Table 2, during normal operation, the control signal to eachof switches 2814-2817 may include a PWM signal determined based onposition information, phase current information, any other suitableinformation, or any combination thereof. For example, the control systemexecutes a feedback control loop for current for each phase bydetermining a least norm current solution for all phase currents toachieve a desired electromagnetic force.

As shown in Table 2, during Braking A, the control signal to each ofswitches 2814-2817 may include a braking signal, which may be, but neednot be, independent of position or current information. Referencingoperation during.

Braking A, the low-voltage switches (i.e., switches 2815 and 2817 asshown in FIG. 28) are closed according to a non-zero braking signal,while the high-voltage switches (i.e., switches 2814 and 2816 as shownin FIG. 28) are maintained open according to a zero braking signal. Toillustrate, during braking A, current loop 2891 is formed, which allowscurrent to flow and dissipate energy to the low-voltage bus line.Because braking signal 2702 includes both on and off intervals, theenergy transfer from phase 2860 may be non-steady. During Braking A,high-voltage switches 2814 and 2816 are maintained open to preventshort-circuiting between the low and high bus lines of DC bus 2802.

As shown in Table 2, during Braking B, the control signal to each ofswitches 2814-2817 may include a braking signal, which may be, but neednot be, independent of position or current information. Referencingoperation during Braking B, the high-voltage switches (i.e., switches2814 and 2816 as shown in FIG. 28) are closed according to a non-zerobraking signal, while the low-voltage switches (i.e., switches 2815 and2817 as shown in FIG. 28) are maintained open according to a zerobraking signal. To illustrate, during braking A, current loop 2890 isformed, which allows current to flow and dissipate energy to thelow-voltage bus line. Because braking signal 2702 includes both on andoff intervals, the energy transfer from phase 2860 may be non-steady.During Braking B, low-voltage switches 2815 and 2817 are maintained opento prevent short-circuiting between the low and high bus lines of DC bus2802.

In some embodiments, during braking, a control system may switchbetween, or alternate among Braking A and Braking B. For example, thecontrol system may alternate between Braking A and Braking B to preventany switch pair (e.g., low-voltage switch pair or high-voltage switchpair) from overheating, or to otherwise balance the energy transferamong the switches of the H-bridge. In some embodiments, Braking A,Braking B, or both may be included along with other braking techniques(e.g., any of the illustrative techniques of the present disclosure),during braking in response to detecting an event. In some embodiments,in the context of phase coupled in a star configuration, more than onephase may be used to create a current loop (e.g., similar to currentloop 2890 or 2891).

In some embodiments, a linear multiphase electromagnetic machine isconfigured to include an eddy current brake. For example, a magneticfield is generated by one or more phases in a conductive material of atranslator, which generates an eddy current that causes a force thatopposes motion of the translator. FIG. 30 shows a cross-sectional viewof stator 3000 and translator 3012, configured for linear eddy currentbraking, in accordance with some embodiments of the present disclosure.Stator 3000 and translator 3012 are part of a linear multiphaseelectromagnetic machine. Stator 3000 includes phases 3001, 3002, 3003,3004, 3005, 3006, 3007, 3008, 3009, 3010, 3011, and 3012, arrangedaxially along axis 3070. Translator 3012 includes magnet section 3030and conductive sections 3031 and 3032 arranged axially offset frommagnet section 3030. Although not shown in FIG. 30, translator 3012 mayinclude additional conductive sections on the other side of magnetsection 3020 from conductive sections 3031 and 3032 (e.g., such thatmagnet section 3030 is axially between conductive sections). FIG. 31shows a flowchart of illustrative process 3100 for engaging an eddycurrent brake, in accordance with some embodiments of the presentdisclosure. Step 3102 includes detecting an event such as, for example,a fault event or failure event. Step 3104 includes generating an eddycurrent to brake a translator, in response to detecting the event.

A conductive section, in the context of eddy current braking, mayinclude any suitable electrically conductive material. For example, aconductive section (e.g., conductive sections 3031 and 3032) may includealuminum, copper, steel, stainless steel, an alloy, any other suitablematerial, or any combination thereof. In a further example, a conductivesection (e.g., conductive sections 3031 and 3032) may include anysuitable geometric properties such as axial thickness, cross-sectionshape, outer diameter, inner diameter, mounting features (e.g., bossesor recesses), cooling features (e.g., fins, ribs or grooves), any othersuitable geometric properties, or any combination thereof. Toillustrate, the conductive section may include a metal ring affixed to atranslator rod/tube and configured to form a predetermined airgap with astator.

Magnet section 3030 and stator 3000 have an associated air gap 3020,which may be configured to affect electromagnetic interactions. Forexample, air gap 3020 may affect reluctance, a force constant, motorefficiency, and any other suitable operating parameters. Conductivesections 3031 and 3032 and stator 3000 have an associated air gap 3021,which may be configured to affect electromagnetic interactions. Air gap3021 may be the same as, or different from, air gap 3020. For example,air gap 3021 may affect a magnetic field at conductive sections 3031 and3032, an eddy current in conductive sections 3031 and 3032, and anyother suitable operating parameters.

During operation (e.g., both normal operation and braking), magnetsection 3030 may be axially aligned with a subset of phases of stator3000. As illustrated in FIG. 30, for example, magnet section 3030 isaxially aligned with phases 3001-3006, and axially offset from phases3007-3012. Accordingly, phases 3001-3006 may interactelectromagnetically with magnet section 3030, while phases 3007-3012 donot electromagnetically interact with magnet section 3030 significantly.In an illustrative example, phase currents may be applied to phases3001-3006 to generate a braking force on translator 3012.

Conductive sections 3031 and 3032, as illustrated in FIG. 30, areaxially aligned at least partially with phases 3010-3012. Because phases3009-3011 are part of the subset of phases 3007-3012 that are axiallyoffset from magnet section 3030, the current in phases 3009-3011 may beused for eddy current braking. For example, during normal operation inthe absence of conductive sections 3031 and 3032, when translator 3012is at the position illustrated in FIG. 30, phase current need not beapplied to phases 3007-3012. Application of current to phases 3007-3012in this spatial configuration would not produce a significantelectromagnetic force on translator 3012. In a further example, duringnormal operation in the presence of conductive sections 3031 and 3032,when translator 3012 is at the position illustrated in FIG. 30, phasecurrent is not applied to phases 3007-3012 (e.g., which would cause eddycurrent braking). In response to an event being detected, a controlsystem may determine a subset of phases that are axially offset frommagnet section 3030 and axially aligned with conductive sections 3031and 3032 and apply current to those phases (e.g., phases 3009-3011 asillustrated in FIG. 30). In an illustrative example, the control systemmay apply a current to at least one of phases 3009-3011 to generate aneddy current in conductive sections 3031 and 3032 depending on axialalignment (e.g., phase 3009 may be used to generate eddy current inconductive sections 3031 because they are axially aligned). The appliedcurrent may have any suitable temporal character including, for example,a sinusoidal amplitude, a pulsed amplitude, a square-wave amplitude, aconstant amplitude, any other suitable amplitude, or any combinationthereof. As translator 3012 moves axially along axis 3070 duringbraking, the subset of phases that are axially aligned and that areaxially offset may change. Accordingly, the control system may applyphase currents to suitable phases for generating an eddy current. Forexample, the control system may determine phases that have associatednon-zero force constants with respect to magnet section 3030 and deemthose phases as potential phases to apply current for eddy currentbraking. For example, the control system may determine phases that areaxially aligned with conductive section 3031, conductive section 3032,or both, and deem those phases as potential phases to apply current foreddy current braking.

FIG. 32 shows illustrative position-velocity trajectories associatedwith a translator, in accordance with some embodiments of the presentdisclosure. Panel 3200 shows position-velocity trajectory 3201 andposition-velocity trajectory 3202, which includes larger translatorspeeds (e.g., equal to the absolute value of velocity) and a largerstroke (e.g., equal to the difference between apex position 1 and apexposition 2). Position-velocity trajectory 3202 may correspond to arelatively higher-power operating condition of a free-piston machine.Position-velocity trajectories 3201 and 3202 are substantially steadyand correspond to normal operation or otherwise steady operation. Atranslator may move among position-velocity trajectories during normaloperation (e.g., load following), or may remain operating substantiallyat a particular position-velocity trajectory.

Panel 3210 shows position-velocity trajectory 3212 during braking, fromnormal operation to a final velocity of zero (i.e., stopped).Position-velocity trajectory 3212 lessens in both peak velocity andstroke length during each subsequent stroke. In some embodiments,position-velocity trajectory 3212 is illustrative of braking processesdisclosed herein.

Panel 3220 shows position-velocity trajectory 3222 during braking, fromnormal operation to a final velocity of zero (i.e., stopped).Position-velocity trajectory 3222 lessens in peak velocity during eachsubsequent stroke. The stroke length of position-velocity trajectory3222 initially increases, and then decreases to zero (i.e., when thevelocity is zero). In some embodiments, position-velocity trajectory3222 is illustrative of braking processes disclosed herein.

Panel 3230 shows position-velocity trajectory 3232 during braking, fromnormal operation to a final velocity of zero (i.e., stopped).Position-velocity trajectory 3232 lessens in peak velocity during eachsubsequent stroke. The stroke length of position-velocity trajectory3232 remains substantially fixed until it decreases to zero (i.e., whenthe velocity is zero). In some embodiments, position-velocity trajectory3232 is illustrative of braking processes disclosed herein.

Panel 3240 shows position-velocity trajectory 3242 during braking,transitioning from a first operating state to a second operating statehaving a lower associated operating power. Position-velocity trajectory3242 lessens in peak velocity and stroke length during the transition.In some embodiments, position-velocity trajectory 3242 is illustrativeof braking processes disclosed herein.

It will be understood that position-velocity trajectories 3201, 3202,3212, 3222, 3232, and 3242 are merely illustrative, and that atranslator may achieve any suitable trajectory during normal operationand braking, in accordance with present disclosure. For example, in someembodiments, a translator undergoing braking may slow down over manycycles (e.g., more than shown in FIG. 32), one cycle, or any suitablenumber of cycles or a portion thereof. In a further example, the endstate of the braking trajectory may be fully-stopped (e.g., a velocityof zero), or an operating condition having a relatively smaller velocity(i.e., lower kinetic energy), stroke length, or a combination thereof.

The above-described embodiments of the present disclosure are presentedfor purposes of illustration and not of limitation, and the presentdisclosure is limited only by the claims that follow. Additionally, itshould be noted that any of the systems, devices or equipment disclosedherein may be used to perform one or more of the steps of any processdisclosed herein. For example, an of the illustrative LEM topologies ofFIGS. 4-7 may be used in connection with any of the systems andprocesses described in the context of FIGS. 9-32. Furthermore, it shouldbe noted that the features and limitations described in any oneembodiment may be applied to any other embodiment herein, and flowchartsor examples relating to one embodiment may be combined with any otherembodiments in a suitable manner, done in different orders, performedwith addition steps, performed with omitted steps, or done in parallel.For example, each of these steps may be performed in any order or inparallel or substantially simultaneously to reduce lag or increase thespeed of the system or method. In addition, the systems and methodsdescribed herein may be performed in real time. It should also be notedthat the systems and/or methods described above may be applied to, orused in accordance with, other systems and/or methods.

It will be understood that the present disclosure is not limited to theembodiments described herein and can be implemented in the context ofany suitable system. In some suitable embodiments, the presentdisclosure is applicable to reciprocating engines and compressors. Insome embodiments, the present disclosure is applicable to free-pistonengines and compressors. In some embodiments, the present disclosure isapplicable to combustion and reaction devices such as a reciprocatingengine and a free-piston engine. In some embodiments, the presentdisclosure is applicable to non-combustion and non-reaction devices suchas reciprocating compressors and free-piston compressors. In someembodiments, the present disclosure is applicable to gas springs. Insome embodiments, the present disclosure is applicable to oil-freereciprocating and free-piston engines and compressors. In someembodiments, the present disclosure is applicable to oil-freefree-piston engines with internal or external combustion or reactions.In some embodiments, the present disclosure is applicable to oil-freefree-piston engines that operate with compression ignition, sparkignition, or both. In some embodiments, the present disclosure isapplicable to oil-free free-piston engines that operate with gaseousfuels, liquid fuels, or both. In some embodiments, the presentdisclosure is applicable to linear free-piston engines. In someembodiments, the present disclosure is applicable to engines that can becombustion engines with internal combustion/reaction or any type of heatengine with external heat addition (e.g., from a heat source or externalreaction such as combustion).

The foregoing is merely illustrative of the principles of thisdisclosure and various modifications may be made by those skilled in theart without departing from the scope of this disclosure. Theabove-described embodiments are presented for purposes of illustrationand not of limitation. The present disclosure also can take many formsother than those explicitly described herein. Accordingly, it isemphasized that this disclosure is not limited to the explicitlydisclosed methods, systems, and apparatuses, but is intended to includevariations to and modifications thereof, which are within the spirit ofthe following claims.

What is claimed is:
 1. A linear generator comprising: a linearelectromagnetic machine (LEM) comprising: a translator, and a statorcomprising a plurality of phases, wherein each phase of the plurality ofphases comprises a respective first phase lead and a respective secondphase lead; a power electronics system coupled to at least one phase ofthe plurality of phases and coupled to a DC bus, the power electronicssystem comprising at least one first switch and at least one secondswitch, wherein each first phase lead is coupled to the at least onefirst switch, and wherein each second phase lead is coupled to that atleast one second switch; and a first phase controller coupled to thepower electronics system and configured to, in response to an event:apply braking signals to the at least one first switch to cause thetranslator to brake, and send a communication signal to a second phasecontroller indicating that braking has occurred.
 2. The linear generatorof claim 1, wherein the event is selected from at least one of: an eventassociated with a controller; an event associated with an encoder; anevent associated with a switch coupled to a phase of the plurality ofphases; an event associated with a grid-tie inverter; an eventassociated with a shorted phase of the plurality of phases; an eventassociated with communication between one or more control subsystems; oran event associated with an operating parameter value of the LEM.
 3. Thelinear generator of claim 1, wherein the event is a lack ofcommunication associated with the first phase controller.
 4. The lineargenerator of claim 1, wherein the at least one first switch comprise afirst high-voltage switch and a first low-voltage switch, wherein the atleast one second switch comprise a second high-voltage switch and asecond low-voltage switch, and wherein the braking signals areconfigured to cause: a first state wherein a first high-voltage switchand a second high-voltage switch are closed for a first time period; asecond state wherein a first low-voltage switch and a second low-voltageswitch are closed for a second time period that does not overlap thefirst time period; and a third state wherein the first high-voltageswitch, the second high-voltage switch, the first low-voltage switch,and the second low-voltage switch are all open for a third time periodthat does not overlap the first time period or the second time period.5. The linear generator of claim 1, wherein the first phase controlleris further configured to apply the braking signals independent ofposition information of the translator.
 6. The linear generator of claim1, wherein the first phase controller is further configured to apply thebraking signals independent of phase current information of each phaseof the plurality of phases of the LEM.
 7. The linear generator of claim1, wherein the first phase controller is further configured to, inresponse to the event, send a communication signal to a third phasecontroller indicating that braking has occurred.
 8. The linear generatorof claim 1, wherein the at least one first switch comprise a firsthigh-voltage switch and a first low-voltage switch, wherein the at leastone second switch comprise a second high-voltage switch and a secondlow-voltage switch, wherein the braking signals comprise at least oneof: a first set of signals comprising: a first signal applied toactivate both the first high-voltage switch and the second high-voltageswitch for a first time period, and to open the first high-voltageswitch and the second high-voltage switch for a second time period, anda second signal applied to open both the first low-voltage switch andthe second low-voltage switch during both the first time period and thesecond time period; or a second set of signals comprising: a thirdsignal applied to activate both the first low-voltage switch and thesecond low-voltage switch for a third time period, and to open the firstlow-voltage switch and the second low-voltage switch for a fourth timeperiod, and a fourth signal applied to open both the first high-voltageswitch and the second high-voltage switch during both the third timeperiod and the fourth time period.
 9. A method for braking a translatorof a linear multiphase electromagnetic machine (LEM), wherein: eachphase of the LEM comprises a respective first phase lead and arespective second phase lead; each first phase lead is coupled to atleast one first switch coupled across a DC bus; each second phase leadis coupled to at least one second switch coupled across the DC bus, themethod comprising: detecting an event; and in response to detecting theevent: automatically communicating, using control circuitry, brakingsignals to the at least one first switch to cause the translator tobrake, and sending a communication signal to a second phase controllerindicating that braking has occurred.
 10. The method of claim 9, whereinthe event is selected from at least one of: an event associated with acontroller; an event associated with an encoder; an event associatedwith a switch coupled to a phase of the plurality of phases; an eventassociated with a grid-tie inverter; an event associated with a shortedphase of the plurality of phases; an event associated with communicationbetween one or more control subsystems; or an event associated with anoperating parameter value of the LEM.
 11. The method of claim 9, whereinthe event is a lack of communication associated with the first phasecontroller.
 12. The method of claim 9, wherein the at least one firstswitch comprise a first high-voltage switch and a first low-voltageswitch, wherein the at least one second switch comprise a secondhigh-voltage switch and a second low-voltage switch, whereincommunicating the braking signals comprises causing: a first statewherein a first high-voltage switch and a second high-voltage switch areclosed for a first time period; a second state wherein a firstlow-voltage switch and a second low-voltage switch are closed for asecond time period that does not overlap the first time period; and athird state wherein the first high-voltage switch, the secondhigh-voltage switch, the first low-voltage switch, and the secondlow-voltage switch are all open for a third time period that does notoverlap the first time period or the second time period.
 13. The methodof claim 9, wherein communicating the braking signals is independent ofposition information of the translator.
 14. The method of claim 9,wherein communicating the braking signals is independent of phasecurrent information of each phase of the plurality of phases.
 15. Themethod of claim 9, further comprising transmitting a communicationsignal to a third phase controller indicating that the braking hasoccurred.
 16. The method of claim 9, wherein the at least one firstswitch comprise a first high-voltage switch and a first low-voltageswitch, wherein the at least one second switch comprise a secondhigh-voltage switch and a second low-voltage switch, wherein the brakingsignals comprise at least one of: a first set of signals comprising: afirst signal applied to activate both the first high-voltage switch andthe second high-voltage switch for a first time period, and to open thefirst high-voltage switch and the second high-voltage switch for asecond time period, and a second signal applied to open both the firstlow-voltage switch and the second low-voltage switch during both thefirst time period and the second time period; or a second set of signalscomprising: a third signal applied to activate both the firstlow-voltage switch and the second low-voltage switch for a third timeperiod, and to open the first low-voltage switch and the secondlow-voltage switch for a fourth time period, and a fourth signal appliedto open both the first high-voltage switch and the second high-voltageswitch during both the third time period and the fourth time period. 17.A non-transient computer readable medium comprising non-transitorycomputer readable instructions for braking a translator of a linearelectromagnetic machine (LEM), wherein: each phase of the LEM comprisesa respective first phase lead and a respective second phase lead; eachfirst phase lead is coupled to at least one first switch coupled acrossa DC bus; each second phase lead is coupled to at least one secondswitch coupled across the DC bus, the non-transitory computer readableinstructions comprising: an instruction for detecting an event;instructions for, in response to detecting the event: automaticallycommunicating braking signals to the at least one first switch to causethe translator to brake, and sending a communication signal to a secondphase controller indicating that braking has occurred.
 18. Thenon-transient computer readable medium of claim 17, wherein the event isselected from at least one of: an event associated with a controller; anevent associated with an encoder; an event associated with a switchcoupled to a phase of the plurality of phases; an event associated witha grid-tie inverter; an event associated with a shorted phase of theplurality of phases; an event associated with communication between oneor more control subsystems; or an event associated with an operatingparameter value of the LEM.
 19. The non-transient computer readablemedium of claim 17, wherein the event is a lack of communicationassociated with the first phase controller.
 20. The non-transientcomputer readable medium of claim 17, further comprising an instructionfor transmitting a communication signal to a third phase controllerindicating that the braking has occurred.